An Introduction to the History of Science

On the other hand, he looked to the arts, crafts, and occupations as a source of scientific principles. In his survey of learning he found some records of agriculture and likewise of many mechanical arts. Some think them a kind of dishonor. "But if my judgment be of any weight, the use of History Mechanical is, of all others, the most radical and fundamental towards natural philosophy." When the different arts are known, the senses will furnish sufficient concrete material for the information of the understanding. The record of the arts is of most use because it exhibits things in motion, and leads more directly to practice. "Upon this history, therefore, mechanical and illiberal as it may seem (all fineness and daintiness set aside), the greatest diligence must be bestowed." "Again, among the particular arts those are to be preferred which exhibit, alter, and prepare natural bodies and materials of things as agriculture, cooking, chemistry, dyeing; the manufacture of glass, enamel, sugar, gunpowder, artificial fires, paper and the like." Weaving, carpentry, architecture, manufacture of mills, clocks, etc. follow. The purpose is not solely to bring the arts to perfection, but all mechanical experiments should be as streams flowing from all sides into the sea of philosophy.

Shortly after James I came to the throne in 1603, Bacon published his Advancement of Learning. He continued in other writings, however, to develop the organization of knowledge, and in 1623 summed up his plan in the De Augmentis Scientiarum.

A recent writer (Pearson, 1900) has attempted to summarize Bacon's classification of the different branches of learning. When one compares this summary with an outline of the classification of knowledge made by the French monk, Hugo of St. Victor, who stands midway between Isidore of Seville (570-636) and Bacon, some points of resemblance are of course obvious. Moreover, Hugo, like Bacon, insisted on the importance of not being narrowly utilitarian. Men, he says, are often accustomed to value knowledge not on its own account but for what it yields. Thus it is with the arts of husbandry, weaving, painting, and the like, where skill is considered absolutely vain, unless it results in some useful product. If, however, we judged after this fashion of God's wisdom, then, no doubt, the creation would be preferred to the Creator. But wisdom is life, and the love of wisdom is the joy of life (felicitas vitæ).

Nevertheless, when we compare these classifications diligently, we find very marked differences between Bacon's views and the medieval. The weakest part of Hugo's classification is that which deals with natural philosophy. Physica, he says, undertakes the investigation of the causes of things in their effects, and of effects in their causes. It deals with the explanation of earthquakes, tides, the virtues of plants, the fierce instincts of wild animals, every species of stone, shrub, and reptile. When we turn to his special work, however, on this branch of knowledge, Concerning Beasts and Other Things, we find no attempt to subdivide the field of physica, but a series of details in botany, geology, zoölogy, and human anatomy, mostly arranged in dictionary form.

When we refer to Bacon's classification we find that Physics corresponds to Hugo's Physica. It studies natural phenomena in relation to their material causes. For this study, Natural History, according to Bacon, supplies the facts. Let us glance, then, at his work on natural history, and see how far he had advanced from the medieval toward the modern conception of the sciences.

For purposes of scientific study he divided the phenomena of the universe into (1) Celestial phenomena; (2) Atmosphere; (3) Globe; (4) Substance of earth, air, fire, water; (5) Genera, species, etc. Great scope is given to the natural history of man. The arts are classified as nature modified by man. History means, of course, descriptive science.

Bacon's Catalogue of Particular Histories by Titles (1620)

1. History of the Heavenly Bodies; or Astronomical History.
2. History of the Configuration of the Heavens and the parts thereof towards the Earth and the parts thereof; or Cosmographical History.
3. History of Comets.
4. History of Fiery Meteors.
5. History of Lightnings, Thunderbolts, Thunders, and Coruscations.
6. History of Winds and Sudden Blasts and Undulations of the Air.
7. History of Rainbows.
8. History of Clouds, as they are seen above.
9. History of the Blue Expanse, of Twilight, of Mock-Suns, Mock-Moons, Haloes, various colours of the Sun; and of every variety in the aspect of the heavens caused by the medium.
10. History of Showers, Ordinary, Stormy, and Prodigious; also of Waterspouts (as they are called); and the like.
11. History of Hail, Snow, Frost, Hoar-frost, Fog, Dew, and the like.
12. History of all other things that fall or descend from above, and that are generated in the upper region.
13. History of Sounds in the upper region (if there be any), besides Thunder.
14. History of Air as a whole, or in the Configuration of the World.
15. History of the Seasons or Temperatures of the Year, as well according to the variations of Regions as according to accidents of Times and Periods of Years; of Floods, Heats, Droughts, and the like.
16. History of Earth and Sea; of the Shape and Compass of them, and their Configurations compared with each other; and of their broadening or narrowing; of Islands in the Sea; of Gulfs of the Sea, and Salt Lakes within the Land; Isthmuses and Promontories.
17. History of the Motions (if any be) of the Globe of Earth and Sea; and of the Experiments from which such motions may be collected.
18. History of the greater motions and Perturbations in Earth and Sea; Earthquakes, Tremblings and Yawnings of the Earth, Islands newly appearing; Floating Islands; Breakings off of Land by entrance of the Sea, Encroachments and Inundations and contrariwise Recessions of the Sea; Eruptions of Fire from the Earth; Sudden Eruptions of Waters from the Earth; and the like.
19. Natural History of Geography; of Mountains, Vallies, Woods, Plains, Sands, Marshes, Lakes, Rivers, Torrents, Springs, and every variety of their course, and the like; leaving apart Nations, Provinces, Cities, and such like matters pertaining to Civil life.
20. History of Ebbs and Flows of the Sea; Currents, Undulations, and other Motions of the Sea.
21. History of other Accidents of the Sea; its Saltness, its various Colours, its Depth; also of Rocks, Mountains, and Vallies under the Sea, and the like.

    Next come Histories of the Greater Masses

22. History of Flame and of things Ignited.
23. History of Air, in Substance, not in the Configuration of the World.
24. History of Water, in Substance, not in the Configuration of the World.
25. History of the Earth and the diversity thereof, in Substance, not in the Configuration of the World.

    Next come Histories of Species

26. History of perfect Metals, Gold, Silver; and of the Mines, Veins, Marcasites of the same; also of the Working in the Mines.
27. History of Quicksilver.
28. History of Fossils; as Vitriol, Sulphur, etc.
29. History of Gems; as the Diamond, the Ruby, etc.
30. History of Stones; as Marble, Touchstone, Flint, etc.
31. History of the Magnet.
32. History of Miscellaneous Bodies, which are neither entirely Fossil nor Vegetable; as Salts, Amber, Ambergris, etc.
33. Chemical History of Metals and Minerals.
34. History of Plants, Trees, Shrubs, Herbs; and of their parts, Roots, Stalks, Wood, Leaves, Flowers, Fruits, Seeds, Gums, etc.
35. Chemical History of Vegetables.
36. History of Fishes, and the Parts and Generation of them.
37. History of Birds, and the Parts and Generation of them.
38. History of Quadrupeds, and the Parts and Generation of them.
39. History of Serpents, Worms, Flies, and other insects; and of the Parts and Generation of them.
40. Chemical History of the things which are taken by Animals.

    Next come Histories of Man

41. History of the Figure and External Limbs of man, his Stature, Frame, Countenance, and Features; and of the variety of the same according to Races and Climates, or other smaller differences.
42. Physiognomical History of the same.
43. Anatomical History, or of the Internal Members of Man; and of the variety of them, as it is found in the Natural Frame and Structure, and not merely as regards Diseases and Accidents out of the course of Nature.
44. History of the parts of Uniform Structure in Man; as Flesh, Bones, Membranes, etc.
45. History of Humours in Man; Blood, Bile, Seed, etc.
46. History of Excrements; Spittle, Urine, Sweats, Stools, Hair of the Head, Hairs of the Body, Whitlows, Nails, and the like.
47. History of Faculties; Attraction, Digestion, Retention, Expulsion, Sanguification, Assimilation of Aliment into the members, conversion of Blood and Flower of Blood into Spirit, etc.
48. History of Natural and Involuntary Motions; as Motion of the Heart, the Pulses, Sneezing, Lungs, Erection, etc.
49. History of Motions partly Natural and Partly Violent; as of Respiration, Cough, Urine, Stool, etc.
50. History of Voluntary Motions; as of the Instruments of Articulation of Words; Motions of the Eyes, Tongue, Jaws, Hands, Fingers; of Swallowing, etc.
51. History of Sleep and Dreams.
52. History of different habits of Body—Fat, Lean; of the Complexions (as they call them), etc.
53. History of the Generation of Man.
54. History of Conception, Vivification, Gestation in the Womb, Birth, etc.
55. History of the Food of Man; and of all things Eatable and Drinkable; and of all Diet; and of the variety of the same according to nations and smaller differences.
56. History of the Growth and Increase of the Body, in the whole and in its parts.
57. History of the Course of Age; Infancy, Boyhood, Youth, Old Age; of Length and Shortness of Life, and the like, according to nations and lesser differences.
58. History of Life and Death.
59. History Medicinal of Diseases, and of the Symptoms and Signs of them.
60. History Medicinal of the Treatment and Remedies and Cures of Diseases.
61. History Medicinal of those things which preserve the Body and the Health.
62. History Medicinal of those things which relate to the Form and Comeliness of the Body.
63. History Medicinal of those things which alter the Body, and pertain to Alterative Regimen.
64. History of Drugs.
65. History of Surgery.
66. Chemical History of Medicines.
67. History of Vision, and of things Visible.
68. History of Painting, Sculpture, Modelling, etc.
69. History of Hearing and Sound.
70. History of Music.
71. History of Smell and Smells.
72. History of Taste and Tastes.
73. History of Touch, and the objects of Touch.
74. History of Venus, as a species of Touch.
75. History of Bodily Pains, as species of Touch.
76. History of Pleasure and Pain in general.
77. History of the Affections; as Anger, Love, Shame, etc.
78. History of the Intellectual Faculties; Reflexion, Imagination, Discourse, Memory, etc.
79. History of Natural Divinations.
80. History of Diagnostics, or Secret Natural Judgements.
81. History of Cookery, and of the arts thereto belonging, as of the Butcher, Poulterer, etc.
82. History of Baking, and the Making of Bread, and the arts thereto belonging, as of the Miller, etc.
83. History of Wine.
84. History of the Cellar and of different kinds of Drink.
85. History of Sweetmeats and Confections.
86. History of Honey.
87. History of Sugar.
88. History of the Dairy.
89. History of Baths and Ointments.
90. Miscellaneous History concerning the care of the body—as of Barbers, Perfumers, etc.
91. History of the working of Gold, and the arts thereto belonging.
92. History of the manufactures of Wool, and the arts thereto belonging.
93. History of the manufactures of Silk, and the arts thereto belonging.
94. History of the manufactures of Flax, Hemp, Cotton, Hair, and other kinds of Thread, and the arts thereto belonging.
95. History of manufactures of Feathers.
96. History of Weaving, and the arts thereto belonging.
97. History of Dyeing.
98. History of Leather-making, Tanning, and the arts thereto belonging.
99. History of Ticking and Feathers.
100. History of working in Iron.
101. History of Stone-cutting.
102. History of the making of Bricks and Tiles.
103. History of Pottery.
104. History of Cements, etc.
105. History of working in Wood.
106. History of working in Lead.
107. History of Glass and all vitreous substances, and of Glass-making.
108. History of Architecture generally.
109. History of Waggons, Chariots, Litters, etc.
110. History of Printing, of Books, of Writing, of Sealing; of Ink, Pen, Paper, Parchment, etc.
111. History of Wax.
112. History of Basket-making.
113. History of Mat-making, and of manufactures of Straw, Rushes, and the like.
114. History of Washing, Scouring, etc.
115. History of Agriculture, Pasturage, Culture of Woods, etc.
116. History of Gardening.
117. History of Fishing.
118. History of Hunting and Fowling.
119. History of the Art of War, and of the arts thereto belonging, as Armoury, Bow-making, Arrow-making, Musketry, Ordnance, Cross-bows, Machines, etc.
120. History of the Art of Navigation, and of the crafts and arts thereto belonging.
121. History of Athletics and Human Exercises of all kinds.
122. History of Horsemanship.
123. History of Games of all kinds.
124. History of Jugglers and Mountebanks.
125. Miscellaneous History of various Artificial Materials,—Enamel, Porcelain, various cements, etc.
126. History of Salts.
127. Miscellaneous History of various Machines and Motions.
128. Miscellaneous History of Common Experiments which have not grown into an Art.

     Histories must also be written of Pure Mathematics; though they are rather observations than experiments

129. History of the Natures and Powers of Numbers.
130. History of the Natures and Powers of Figures.

The fragment containing this catalogue (Parasceve—Day of Preparation) was added to Bacon's work on method, The New Logic (Novum Organum), 1620. Besides completing his survey and classification of the sciences (De Augmentis Scientiarum), 1623, he published a few separate writings on topics in the catalogue—Winds, Life and Death, Tides, etc. In 1627, a year after his death, appeared his much misunderstood work, Sylva Sylvarum. He had found that the Latin word sylva meant stuff or raw material, as well as a wood, and called this final work Sylva Sylvarum, which I would translate, "Jungle of Raw Material." He himself referred to it as "an undigested heap of particulars"; yet he was willing it should be published because "he preferred the good of men to anything that might have relation to himself." In it, following his catalogue, he fulfilled the promise made in 1620, of putting nature and the arts to question. Some of the problems suggested for investigation are: congealing of air, turning air into water, the secret nature of flame, motion of gravity, production of cold, nourishing of young creatures in the egg or womb, prolongation of life, the media of sound, infectious diseases, accelerating and preventing putrefaction, accelerating and staying growth, producing fruit without core or seed, production of composts and helps for ground, flying in the air.

In the New Atlantis, a work of imagination, Bacon had represented as already achieved for mankind some of the benefits he wished for: artificial metals, various cements, excellent dyes, animals for vivisection and medical experiment, instruments which generate heat solely by motion, artificial precious stones, conveyance of sound for great distances and in tortuous lines, new explosives. "We imitate," says the guide in the Utopian land, "also flights of birds; we have some degree of flying in the air; we have ships and boats for going under water." Bacon believed in honoring the great discoverers and inventors, and advocated maintaining a calendar of inventions.

He was a fertile and stimulating thinker, and much of his great influence arose from the comprehensiveness that led to his celebrated classification of the sciences.

REFERENCES

CHAPTER VI

SCIENTIFIC METHOD—GILBERT, GALILEO, HARVEY, DESCARTES

The previous chapter has given some indication of the range of the material which was demanding scientific investigation at the end of the sixteenth and the beginning of the seventeenth century. The same period witnessed a conscious development of the method, or methods, of investigation. As we have seen, Bacon wrote in 1620 a considerable work, The New Logic (Novum Organum), so called to distinguish it from the traditional deductive logic. It aimed to furnish the organ or instrument, to indicate the correct mental procedure, to be employed in the discovery of natural law. Some seventeen years later, the illustrious Frenchman René Descartes (1596-1650) published his Discourse on the Method of rightly conducting the Reason and seeking Truth in the Sciences. Both of these philosophers illustrated by their own investigations the efficiency of the methods which they advocated.

Before 1620, however, the experimental method had already yielded brilliant results in the hands of other scientists. We pass over Leonardo da Vinci and many others in Italy and elsewhere, whose names should be mentioned if we were tracing this method to its origin. By 1600 William Gilbert (1540-1603), physician to Queen Elizabeth, before whom, as a picture in his birthplace illustrates, he was called to demonstrate his discoveries, had published his work on the Magnet, the outcome of about eighteen years of critical research. He may be considered the founder of electrical science. Galileo, who discovered the fundamental principles of dynamics and thus laid the basis of modern physical science, although he did not publish his most important work till 1638, had even before the close of the sixteenth century prepared the way for the announcement of his principles by years of strict experiment. By the year 1616, William Harvey (1578-1657), physician at the court of James I, and, later, of Charles I, had, as the first modern experimental physiologist, gained important results through his study of the circulation of the blood.

It is not without significance that both Gilbert and Harvey had spent years in Italy, where, as we have implied, the experimental method of scientific research was early developed. Harvey was at Padua (1598-1602) within the time of Galileo's popular professoriate, and may well have been inspired by the physicist to explain on dynamical principles the flow of blood through arteries and veins. This conjecture is the more probable, since Galileo, like Harvey and Gilbert, had been trained in the study of medicine. Bacon in turn had in his youth learned something of the experimental method on the Continent of Europe, and, later, was well aware of the studies of Gilbert and Galileo, as well as of Harvey, who was indeed his personal physician.

Although these facts seem to indicate that method may be transmitted in a nation or a profession, or through personal association, there still remains some doubt as to whether anything so intimate as the mental procedure involved in invention and in the discovery of truth can be successfully imparted by instruction. The individuality of the man of genius engaged in investigation must remain a factor difficult to analyze. Bacon, whose purpose was to hasten man's empire over nature through increasing the number of inventions and discoveries, recognized that the method he illustrated is not the sole method of scientific investigation. In fact, he definitely states that the method set forth in the Novum Organum is not original, or perfect, or indispensable. He was aware that his method tended to the ignoring of genius and to the putting of intelligences on one level. He knew that, although it is desirable for the investigator to free his mind from prepossessions, and to avoid premature generalizations, interpretation is the true and natural work of the mind when free from impediments, and that the conjecture of the man of genius must at times anticipate the slow process of painful induction. As we shall see in the nineteenth chapter, the psychology of to-day does not know enough about the workings of the mind to prescribe a fixed mental attitude for the investigator. Nevertheless, Bacon was not wrong in pointing out the virtues of a method which he and many others turned to good account. Let us first glance, however, at the activities of those scientists who preceded Bacon in the employment of the experimental method.

Gilbert relied, in his investigations, on oft-repeated and verifiable experiments, as can be seen from his work De Magnete. He directs the experimenter, for example, to take a piece of loadstone of convenient size and turn it on a lathe to the form of a ball. It then may be called a terrella, or earthkin. Place on it a piece of iron wire. The ends of the wire move round its middle point and suddenly come to a standstill. Mark with chalk the line along which the wire lies still and sticks. Then move the wire to other spots on the terrella and repeat your procedure. The lines thus marked, if produced, will form meridians, all coming together at the poles. Again, place the magnet in a wooden vessel, and then set the vessel afloat in a tub or cistern of still water. The north pole of the stone will seek approximately the direction of the south pole of the earth, etc. It was on the basis of scores of experiments of this sort, carried on from about 1582 till 1600, that Gilbert felt justified in concluding that the terrestrial globe is a magnet. This theory has since that time been abundantly confirmed by navigators. The full title of his book is Concerning the Magnet and Magnetic Bodies, and concerning the Great Magnet the Earth: A New Natural History (Physiologia) demonstrated by many Arguments and Experiments. It does not detract from the credit of Gilbert's result to state that his initial purpose was not to discover the nature of magnetism or electricity, but to determine the true substance of the earth, the innermost constitution of the globe. He was fully conscious of his own method and speaks with scorn of certain writers who, having made no magnetical experiments, constructed ratiocinations on the basis of mere opinions and old-womanishly dreamed the things that were not.

Galileo (1564-1642) even as a child displayed something of the inventor's ingenuity, and when he was nineteen, shortly after the beginning of Gilbert's experiments, his keen perception for the phenomena of motion led to his making a discovery of great scientific moment. He observed a lamp swinging by a long chain in the cathedral of his native city of Pisa, and noticed that, no matter how much the range of the oscillations might vary, their times were constant. He verified his first impressions by counting his pulse, the only available timepiece. Later he invented simple pendulum devices for timing the pulse of patients, and even made some advances in applying his discovery in the construction of pendulum clocks.

In 1589 he was appointed professor of mathematics in the University of Pisa, and within a year or two established through experiment the foundations of the science of dynamics. As early as 1590 he put on record, in a Latin treatise Concerning Motion (De Motu), his dissent from the theories of Aristotle in reference to moving bodies, confuting the Philosopher both by reason and ocular demonstration. Aristotle had held that two moving bodies of the same sort and in the same medium have velocities in proportion to their weights. If a moving body, whose weight is represented by b, be carried through the line c—e which is divided in the point d, if, also, the moving body is divided according to the same proportion as line c—e is in the point d, it is manifest that in the time taken to carry the whole body through c—e, the part will be moved through c—d. Galileo said that it is as clear as daylight that this view is ridiculous, for who would believe that when two lead spheres are dropped from a great height, the one being a hundred times heavier than the other, if the larger took an hour to reach the earth, the smaller would take a hundred hours? Or, that if from a high tower two stones, one twice the weight of the other, should be pushed out at the same moment, the larger would strike the ground while the smaller was still midway? His biography tells that Galileo in the presence of professors and students dropped bodies of different weights from the height of the Leaning Tower of Pisa to demonstrate the truth of his views. If allowance be made for the friction of the air, all bodies fall from the same height in equal times: the final velocities are proportional to the times; the spaces passed through are proportional to the squares of the times. The experimental basis of the last two statements was furnished by means of an inclined plane, down a smooth groove in which a bronze ball was allowed to pass, the time being ascertained by means of an improvised water-clock.

Galileo's mature views on dynamics received expression in a work published in 1638, Mathematical Discourses and Demonstrations concerning Two New Sciences relating to Mechanics and Local Movements. It treats of cohesion and resistance to fracture (strength of materials), and uniform, accelerated, and projectile motion (dynamics). The discussion is in conversation form. The opening sentence shows Galileo's tendency to base theory on the empirical. It might be freely translated thus: "Large scope for intellectual speculation, I should think, would be afforded, gentlemen, by frequent visits to your famous Venetian Dockyard (arsenale), especially that part where mechanics are in demand; seeing that there every sort of instrument and machine is put to use by numbers of workmen, among whom, taught both by tradition and their own observation, there must be some very skillful and also able to talk." The view of the shipbuilders, that a large galley before being set afloat is in greater danger of breaking under its own weight than a small galley, is the starting-point of this most important of Galileo's contributions to science.

Vesalius (1514-1564) had in his work on the structure of the human body (De Humani Corporis Fabrica, 1543) shaken the authority of Galen's anatomy; it remained for Harvey on the basis of the new anatomy to improve upon the Greek physician's experimental physiology. Harvey professed to learn and teach anatomy, not from books, but from dissections, not from the dogmas of the philosophers, but from the fabric of nature.

There have come down to us notes of his lectures on anatomy delivered first in 1616. A brief extract will show that even at that date he had already formulated a theory of the circulation of the blood:—

"[1] By the structure of the heart it appears that the blood is continually transfused through the lungs to the aorta—as by the two clacks of a water-ram for raising water.

"It is shown by ligature that there is continuous motion of the blood from arteries to veins.

"Whence Δ it is demonstrated that there is a continuous motion of the blood in a circle, affected by the beat of the heart."

It was not till 1628 that Harvey published his Anatomical Disquisition on the Motion of the Heart and Blood in Animals. It gives the experimental basis of his conclusions. If a live snake be laid open, the heart will be seen pulsating and propelling its contents. Compress the large vein entering the heart, and the part intervening between the point of constriction and the heart becomes empty and the organ pales and shrinks. Remove the pressure, and the size and color of the heart are restored. Now compress the artery leading from the organ, and the part between the heart and the point of pressure, and the heart itself, become distended and take on a deep purple color. The course of the blood is evidently from the vena cava through the heart to the aorta. Harvey in his investigations made use of many species of animals—at least eighty-seven.

It was believed by some, before Harvey's demonstrations, that the arteries were hollow pipes carrying air from the lungs throughout the body, although Galen had shown by cutting a dog's trachea, inflating the lungs and tying the trachea, that the lungs were in an enclosing sack which retained the air. Harvey, following Galen, held that the pulmonary artery, carrying blood to the lungs from the right side of the heart, and the pulmonary veins, carrying blood from the lungs to the left side of the heart, intercommunicate in the hidden porosities of the lungs and through minute inosculations.

In man the vena cava carries the blood to the right side of the heart, the pulmonary artery inosculates with the pulmonary veins, which convey it to the left side of the heart. This muscular pump drives it into the aorta. It still remains to be shown that in the limbs the blood passes from the arteries to the veins. Bandage the arm so tightly that no pulse is felt at the wrist. The hand appears at first natural, and then grows cold. Loose the bandage sufficiently to restore the pulse. The hand and forearm become suffused and swollen. In the first place the supply of blood from the deep-lying arteries is cut off. In the second case the blood returning by the superficial veins is dammed back. In the limbs as in the lungs the blood passes from artery to vein by anastomoses and porosities. All these arteries have their source in the aorta; all these veins pour their stream ultimately into the vena cava. The veins have valves, which prevent the blood flowing except toward the heart. Again, the veins and arteries form a connected system; for through either a vein or an artery all the blood may be drained off. The arguments by which Harvey supported his view were various. The opening clause of his first chapter, "When I first gave my mind to vivisection as a means of discovering the motions and uses of the heart," throws a strong light on his special method of experimental investigation.

Bacon, stimulated by what he called philanthropia, always aimed, as we have seen, to establish man's control over nature. But all power of a high order depends on an understanding of the essential character, or law, of heat, light, sound, gravity, and the like. Nothing short of a knowledge of the underlying nature of phenomena can give science advantage over chance in hitting upon useful discoveries and inventions. It is, therefore, natural to find him applying his method of induction—his special method of true induction—to the investigation of heat.

In the first place, let there be mustered, without premature speculation, all the instances in which heat is manifested—flame, lightning, sun's rays, quicklime sprinkled with water, damp hay, animal heat, hot liquids, bodies subjected to friction. Add to these, instances in which heat seems to be absent, as moon's rays, sun's rays on mountains, oblique rays in the polar circle. Try the experiment of concentrating on a thermoscope, by means of a burning-glass, the moon's rays. Try with the burning-glass to concentrate heat from hot iron, from common flame, from boiling water. Try a concave glass with the sun's rays to see whether a diminution of heat results. Then make record of other instances, in which heat is found in varying degrees. For example, an anvil grows hot under the hammer. A thin plate of metal under continuous blows might grow red like ignited iron. Let this be tried as an experiment.

After the presentation of these instances induction itself must be set to work to find out what factor is ever present in the positive instances, what factor is ever wanting in the negative instances, what factor always varies in the instances which show variation. According to Bacon it is in the process of exclusion that the foundations of true induction are laid. We can be certain, for example, that the essential nature of heat does not consist in light and brightness, since it is present in boiling water and absent in the moon's rays.

The induction, however, is not complete till something positive is established. At this point in the investigation it is permissible to venture an hypothesis in reference to the essential character of heat. From a survey of the instances, all and each, it appears that the nature of which heat is a particular case is motion. This is suggested by flame, simmering liquids, the excitement of heat by motion, the extinction of fire by compression, etc. Motion is the genus of which heat is the species. Heat itself, its essence, is motion and nothing else.

It remains to establish its specific differences. This accomplished, we arrive at the definition: Heat is a motion, expansive, restrained, and acting in its strife upon the smaller particles of bodies. Bacon, glancing toward the application of this discovery, adds: "If in any natural body you can excite a dilating or expanding motion, and can so repress this motion and turn it back upon itself, that the dilation shall not proceed equally, but have its way in one part and be counteracted in another, you will undoubtedly generate heat." The reader will recall that Bacon looked for the invention of instruments that would generate heat solely by motion.

Descartes was a philosopher and mathematician. In his Discourse on Method and his Rules for the Direction of the Mind (1628) he laid emphasis on deduction rather than on induction. In the subordination of particulars to general principles he experienced a satisfaction akin to the sense of beauty or the joy of artistic production. He speaks enthusiastically of that pleasure which one feels in truth, and which in this world is about the only pure and unmixed happiness.

At the same time he shared Bacon's distrust of the Aristotelian logic and maintained that ordinary dialectic is valueless for those who desire to investigate the truth of things. There is need of a method for finding out the truth. He compares himself to a smith forced to begin at the beginning by fashioning tools with which to work.

In his method of discovery he determined to accept nothing as true that he did not clearly recognize to be so. He stood against assumptions, and insisted on rigid proof. Trust only what is completely known. Attain a certitude equal to that of arithmetic and geometry. This attitude of strict criticism is characteristic of the scientific mind.

Again, Descartes was bent on analyzing each difficulty in order to solve it; to neglect no intermediate steps in the deduction, but to make the enumeration of details adequate and methodical. Preserve a certain order; do not attempt to jump from the ground to the gable, but rise gradually from what is simple and easily understood.

Descartes' interest was not in the several branches of mathematics; rather he wished to establish a universal mathematics, a general science relating to order and measurement. He considered all physical nature, including the human body, as a mechanism, capable of explanation on mathematical principles. But his immediate interest lay in numerical relationships and geometrical proportions.

Recognizing that the understanding was dependent on the other powers of the mind, Descartes resorted in his mathematical demonstrations to the use of lines, because he could find no method, as he says, more simple or more capable of appealing to the imagination and senses. He considered, however, that in order to bear the relationships in memory or to embrace several at once, it was essential to explain them by certain formulæ, the shorter the better. And for this purpose it was requisite to borrow all that was best in geometrical analysis and algebra, and to correct the errors of one by the other.

Descartes was above all a mathematician, and as such he may be regarded as a forerunner of Newton and other scientists; at the same time he developed an exact scientific method, which he believed applicable to all departments of human thought. "Those long chains of reasoning," he says, "quite simple and easy, which geometers are wont to employ in the accomplishment of their most difficult demonstrations, led me to think that everything which might fall under the cognizance of the human mind might be connected together in the same manner, and that, provided only one should take care not to receive anything as true which was not so, and if one were always careful to preserve the order necessary for deducing one truth from another, there would be none so remote at which he might not at last arrive, or so concealed which he might not discover."

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CHAPTER VII

SCIENCE AS MEASUREMENT—TYCHO BRAHE, KEPLER, BOYLE

Considering the value for clearness of thought of counting, measuring and weighing, it is not surprising to find that in the seventeenth century, and even at the end of the sixteenth, the advance of the sciences was accompanied by increased exactness of measurement and by the invention of instruments of precision. The improvement of the simple microscope, the invention of the compound microscope, of the telescope, the micrometer, the barometer, the thermoscope, the thermometer, the pendulum clock, the improvement of the mural quadrant, sextant, spheres, astrolabes, belong to this period.

Measuring is a sort of counting, and weighing a form of measuring. We may count disparate things whether like or unlike. When we measure or weigh we apply a standard and count the times that the unit—cubit, pound, hour—is found to repeat itself. We apply our measure to uniform extension, meting out the waters by fathoms or space by the sun's diameter, and even subject time to arbitrary divisions. The human mind has been developed through contact with the multiplicity of physical objects, and we find it impossible to think clearly and scientifically about our environment without dividing, weighing, measuring, counting.

In measuring time we cannot rely on our inward impressions; we even criticize these impressions and speak of time as going slowly or quickly. We are compelled in the interests of accuracy to provide an objective standard in the clock, or the revolving earth, or some other measurable thing. Similarly with weight and heat; we cannot rely on the subjective impression, but must devise apparatus to record by a measurable movement the amount of the pressure or the degree of temperature.

"God ordered all things by measure, number, and weight." The scientific mind does not rest satisfied till it is able to see phenomena in their number relationships. Scientific thought is in this sense Pythagorean, that it inquires in reference to quantity and proportion.

As implied in a previous chapter, number relations are not clearly grasped by primitive races. Many primitive languages have no words for numerals higher than five. That fact does not imply that these races do not know the difference between large and small numbers, but precision grows with civilization, with commercial pursuits, and other activities, such as the practice of medicine, to which the use of weights and measures is essential. Scientific accuracy is dependent on words and other means of numerical expression. From the use of fingers and toes, a rude score or tally, knots on a string, or a simple abacus, the race advances to greater refinement of numerical expression and the employment of more and more accurate apparatus.

One of the greatest contributors to this advance was the celebrated Danish astronomer, Tycho Brahe (1546-1601). Before 1597 he had completed his great mural quadrant at the observatory of Uraniborg. He called it with characteristic vanity the Tichonic quadrant. It consisted of a graduated arc of solid polished brass five inches broad, two inches thick, and with a radius of about six and three quarters feet. Each degree was divided into minutes, and each minute into six parts. Each of these parts was then subdivided into ten seconds, which were indicated by dots arranged in transverse oblique lines on the width of brass.

The arc was attached in the observation room to a wall running exactly north, and so secured with screws (firmissimis cochleis) that no force could move it. With its concavity toward the southern sky it was closely comparable, though reverse, to the celestial meridian throughout its length from horizon to zenith. The south wall, above the point where the radii of the quadrant met, was pierced by a cylinder of gilded brass placed in a rectangular opening, which could be opened or closed from the outside. The observation was made through one of two sights that were attached to the graduated arc and could be moved from point to point on it. In the sights were parallel slits, right, left, upper, lower. If the altitude and the transit through the meridian were to be taken at the same time the four directions were to be followed. It was the practice for the student making the observation to read off the number of degrees, minutes, etc., of the angle at which the altitude or transit was observed, so that it might be recorded by a second student. A third took the time from two clock dials when the observer gave the signal, and the exact moment of observation was also recorded by student number two. The clocks recorded minutes and the smaller divisions of time; great care, however, was required to obtain good results from them. There were four clocks in the observatory, of which the largest had three wheels, one wheel of pure solid brass having twelve hundred teeth and a diameter of two cubits.

Lest any space on the wall should lie empty a number of paintings were added: Tycho himself in an easy attitude seated at a table and directing from a book the work of his students. Over his head is an automatic celestial globe invented by Tycho and constructed at his own expense in 1590. Over the globe is a part of Tycho's library. On either side are represented as hanging small pictures of Tycho's patron, Frederick II of Denmark (d. 1588) and Queen Sophia. Then other instruments and rooms of the observatory are pictured; Tycho's students, of whom there were always at least six or eight, not to mention younger pupils. There appears also his great brass globe six feet in diameter. Then there is pictured Tycho's chemical laboratory, on which he has expended much money. Finally comes one of Tycho's hunting dogs—very faithful and sagacious; he serves here as a hieroglyph of his master's nobility as well as of sagacity and fidelity. The expert architect and the two artists who assisted Tycho are delineated in the landscape and even in the setting sun in the top-most part of the painting, and in the decoration above.

The principal use of this largest quadrant was the determination of the angle of elevation of the stars within the sixth part of a minute, the collineation being made by means of one of the sights, the parallel horizontal slits in which were aligned with the corresponding parts of the circumference of the cylinder. The altitude was recorded according to the position of the sight attached to the graduated arc.

Tycho Brahe had a great reverence for Copernicus, but he did not accept his planetary system; and he felt that advance in astronomy depended on painstaking observation. For over twenty years under the kings of Denmark he had good opportunities for pursuing his investigation. The island of Hven became his property. A thoroughly equipped observatory was provided, including printing-press and workshops for the construction of apparatus. As already implied, capable assistants were at the astronomer's command. In 1598, after having left Denmark, Tycho in a splendid illustrated book (Astronomiæ Instauratæ Mechanica) gave an account of this astronomical paradise on the Insula Venusia as he at times called it. The book, prepared for the hands of princes, contains about twenty full-page colored illustrations of astronomical instruments (including, of course, the mural quadrant), of the exterior of the observatory of Uraniborg, etc. The author had a consciousness of his own worth, and deserves the name Tycho the Magnificent. The results that he obtained were not unworthy of the apparatus employed in his observations, and before he died at Prague in 1601, Tycho Brahe had consigned to the worthiest hands the painstaking record of his labors.

Johann Kepler (1571-1630) had been called, as the astronomer's assistant, to the Bohemian capital in 1600 and in a few months fell heir to Tycho's data in reference to 777 stars, which he made the basis of the Rudolphine tables of 1627. Kepler's genius was complementary to that of his predecessor. He was gifted with an imagination to turn observations to account. His astronomy did not rest in mere description, but sought the physical explanation. He had the artist's feeling for the beauty and harmony, which he divined before he demonstrated, in the number relations of the planetary movements. After special studies of Mars based on Tycho's data, he set forth in 1609 (Astronomia Nova) (1) that every planet moves in an ellipse of which the sun occupies one focus, and (2) that the area swept by the radius vector from the planet to the sun is proportional to the time. Luckily for the success of his investigation the planet on which he had concentrated his attention is the one of all the planets then known, the orbit of which most widely differs from a circle. In a later work (Harmonica Mundi, 1619) the title of which, the Harmonics of the Universe, proclaimed his inclination to Pythagorean views, he demonstrated (3) that the square of the periodic time of any planet is proportional to the cube of its mean distance from the sun.

Kepler's studies were facilitated by the invention, in 1614 by John Napier, of logarithms, which have been said, by abridging tedious calculations, to double the life of an astronomer. About the same time Kepler in purchasing some wine was struck by the rough-and-ready method used by the merchant to determine the capacity of the wine-vessels. He applied himself for a few days to the problems of mensuration involved, and in 1615 published his treatise (Stereometria Doliorum) on the cubical contents of casks (or wine-jars), a source of inspiration to all later writers on the accurate determination of the volume of solids. He helped other scientists and was himself richly helped. As early as 1610 there had been presented to him a means of precision of the first importance to the progress of astronomy, namely, a Galilean telescope.

The early history of telescopes shows that the effect of combining two lenses was understood by scientists long before any particular use was made of this knowledge; and that those who are accredited with introducing perspective glasses to the public hit by accident upon the invention. Priority was claimed by two firms of spectacle-makers in Middelburg, Holland, namely, Zacharias, miscalled Jansen, and Lippershey. Galileo heard of the contrivance in July, 1609, and soon furnished so powerful an instrument of discovery that things seen through it appeared more than thirty times nearer and almost a thousand times larger than when seen by the naked eye. He was able to make out the mountains in the moon, the satellites of Jupiter in rotation, the spots on the revolving sun; but his telescope afforded only an imperfect view of Saturn. Of course these facts, published in 1610 (Sidereus Nuncius), strengthened his advocacy of the Copernican system. Galileo laughingly wrote Kepler that the professors of philosophy were afraid to look through his telescope lest they should fall into heresy. The German astronomer, who had years before written on the optics of astronomy, now (1611) produced his Dioptrice, the first satisfactory statement of the theory of the telescope.

About 1639 Gascoigne, a young Englishman, invented the micrometer, which enables an observer to adjust a telescope with very great precision. Before the invention of the micrometer exactitude was impossible, because the adjustment of the instrument depended on the discrimination of the naked eye. The micrometer was a further advance in exact measurement. Gascoigne's determinations of, for example, the diameter of the sun, bear comparison with the findings of even recent astronomical science.

The history of the microscope is closely connected with that of the telescope. In the first half of the seventeenth century the simple microscope came into use. It was developed from the convex lens, which, as we have seen in a previous chapter, had been known for centuries, if not from remote antiquity. With the simple microscope Leeuwenhoek before 1673 had studied the structure of minute animal organisms and ten years later had even obtained sight of bacteria. Very early in the same century Zacharias had presented Prince Maurice, the commander of the Dutch forces, and the Archduke Albert, governor of Holland, with compound microscopes. Kircher (1601-1680) made use of an instrument that represented microscopic forms as one thousand times larger than their actual size, and by means of the compound microscope Malpighi was able in 1661 to see blood flowing from the minute arteries to the minute veins on the lung and on the distended bladder of the live frog. The Italian microscopist thus, among his many achievements, verified by observation what Harvey in 1628 had argued must take place.

In this same epoch apparatus of precision developed in other fields. Weight clocks had been in use as time-measurers since the thirteenth century, but they were, as we have seen, difficult to control and otherwise unreliable. Even in the seventeenth century scientists in their experiments preferred some form of water-clock. In 1636 Galileo, in a letter, mentioned the feasibility of constructing a pendulum clock, and in 1641 he dictated a description of the projected apparatus to his son Vincenzo and to his disciple Viviani. He himself was then blind, and he died the following year. His instructions were never carried into effect. However, in 1657 Christian Huygens applied the pendulum to weight clocks of the old stamp. In 1674 he gave directions for the manufacture of a watch, the movement of which was driven by a spring.

Galileo, to whom the advance in exact science is so largely indebted, must also be credited with the first apparatus for the measurement of temperatures. This was invented before 1603 and consisted of a glass bulb with a long stem of the thickness of a straw. The bulb was first heated and the stem placed in water. The point at which the water, which rose in the tube, might stand was an indication of the temperature. In 1631 Jean Rey just inverted this contrivance, filling the bulb with water. Of course these thermoscopes would register the effect of varying pressures as well as temperatures, and they soon made way for the thermometer and the barometer. Before 1641 a true thermometer was constructed by sealing the top of the tube after driving out the air by heat. Spirits of wine were used in place of water. Mercury was not employed till 1670.

Descartes and Galileo had brought under criticism the ancient idea that nature abhors a vacuum. They knew that the horror vacui was not sufficient to raise water in a pump more than about thirty-three feet. They had also known that air has weight, a fact which soon served to explain the so-called force of suction. Galileo's associate Torricelli reasoned that if the pressure of the air was sufficient to support a column of water thirty-three feet in height, it would support a column of mercury of equal weight. Accordingly in 1643 he made the experiment of filling with mercury a glass tube four feet long closed at the upper end, and then opening the lower end in a basin of mercury. The mercury in the tube sank until its level was about thirty inches above that of the mercury in the basin, leaving a vacuum in the upper part of the tube. As the specific gravity of mercury is 13, Torricelli knew that his supposition had been correct and that the column of mercury in the tube and the column of water in the pump were owing to the pressure or weight of the air.

Pascal thought that this pressure would be less at a high altitude. His supposition was tested on a church steeple at Paris, and, later, on the Puy de Dôme, a mountain in Auvergne. In the latter case a difference of three inches in the column of mercury was shown at the summit and base of the ascent. Later Pascal experimented with the siphon and succeeded in explaining it on the principle of atmospheric pressure.

Torricelli in the space at the top of his barometer (pressure-gauge) had produced what is called a Torricellian vacuum. Otto von Guericke, a burgomaster of Magdeburg, who had traveled in France and Italy, succeeded in constructing an air-pump by means of which air might be exhausted from a vessel. Some of his results became widely known in 1657, though his works were not published till 1673.

Robert Boyle (1626-1691), born at Castle Lismore in Ireland, was the seventh son and fourteenth child of the distinguished first Earl of Cork. He was early acquainted with these various experiments in reference to the air, as well as with Descartes' theory that air is nothing but a congeries or heap of small, and, for the most part, flexible particles. In 1659 he wrote his New Experiments Physico-Mechanical touching the Spring of the Air. Instead of spring, he at times used the word elater (ἐλατὴρ). In this treatise he describes experiments with the improved air-pump constructed at his suggestion by his assistant, Robert Hooke.

One of Boyle's critics, a professor at Louvain, while admitting that air had weight and elasticity, denied that these were sufficient to account for the results ascribed to them. Boyle thereupon published a Defence of the Doctrine touching the Spring and Weight of the Air. He felt able to prove that the elasticity of the air could under circumstances do far more than sustain twenty-nine or thirty inches of mercury. In support of his view he cited a recent experiment.

He had taken a piece of strong glass tubing fully twelve feet in length. (The experiment was made by a well-lighted staircase, the tube being suspended by strings.) The glass was heated more than a foot from the lower end, and bent so that the shorter leg of twelve inches was parallel with the longer. The former was hermetically sealed at the top and marked off in forty-eight quarter-inch spaces. Into the opening of the longer leg, also graduated, mercury was poured. At first only enough was introduced to fill the arch, or bent part of the tube below the graduated legs. The tube was then inclined so that the air might pass from one leg to the other, and equality of pressure at the start be assured. Then more mercury was introduced and every time that the air in the shorter leg was compressed a half or a quarter of an inch, a record was made of the height of the mercury in the long leg of the tube. Boyle reasoned that the compressed air was sustaining the pressure of the column of mercury in the long leg plus the pressure of the atmosphere at the tube's opening, equivalent to 29²⁄₁₆ inches of mercury. Some of the results were as follows: When the air in the short tube was compressed from 12 to 3 inches, it was under a pressure of 117⁹⁄₁₆ inches of mercury; when compressed to 4 it was under pressure of 87¹⁵⁄₁₆ inches of mercury; when compressed to 6, 58¹³⁄₁₆; to 9, 39⁵⁄₈. Of course, when at the beginning of the experiment there were 12 inches of air in the short tube, it was under the pressure of the atmosphere, equal to that of 29²⁄₁₆ inches of mercury. Boyle with characteristic caution was not inclined to draw too general a conclusion from his experiment. However, it was evident, making allowance for some slight irregularity in the experimental results, that air reduced under pressure to one half its original volume, doubles its resistance; and that if it is further reduced to one half,—for example, from six to three inches,—it has four times the resistance of common air. In fact, Boyle had sustained the hypothesis that supposes the pressures and expansions to be in reciprocal proportions.

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