FOOTNOTES:

1 It is well known that ants, by touching the skin of aphides, extract therefrom a secretion of viscous matter, which nourishes them. They will frequently carry off the aphides to their habitations, and keep them there; thus one may say they keep a cow in their stable.
2 The preservation of insects, and their preparation for collections, necessitates some precaution. Entomologists are in the habit of spreading them out on a small board, and arranging the legs and antennæ by means of large pins. The wings should be dried by placing them on strips of paper, which preserves them. These precautions are indispensable if it is wished that the insects in a collection should retain their distinctive characters. Worms and caterpillars can be raised in pots filled with earth, if carefully covered over with muslin or wire gauze with very fine meshes. The process of hatching may give rise to many interesting observations.
3 It frequently happens that in a small aquarium, constructed after this fashion, the animals escape. This is avoided by covering the vase with a net.
4 The infusion of parsley has the advantage of not sensibly obscuring the water.
5 Detailed accounts in Vol. lxxxiii., pp. 243 and 292 of “La Nature.”
6 See “La Nature,” 4th year, 1876, 2nd half-year, p. 167. M. A. Guillemin mentions, in connection with the phenomenon of July 12th, 1876, the presence of light masses of cloud of a greyish-blue colour, similar to those perceived in the phenomena just described.
7 M. A. G. has written us an interesting letter on the subject of similar experiments, which we here transcribe:—

“When a siphon of seltzer water has been opened some little time, and the equilibrium of tension is nearly established between the escaped gas and the dissolved gas, a vertical stream of bubbles is seen to rise from the bottom of the apparatus, which present a very clear example of the law of ascension of bubbles; that is to say (putting out of the question the expansion of the bubbles in their passage upwards), it is an inverse representation of the law of gravity affecting falling bodies. The bubbles, in fact, detach themselves from their starting point with perfect regularity; and as the interval varies in one file from another, we have before us a multiplied representation of that terrible law which Attwood’s machine made such a bugbear to the commercial world. I believe it is possible, by counting the number of bubbles that detach themselves in a second, in each file, and the number which the whole stream contains at a given instant, to carry the verification further; but I must confess that I have not done so myself.”

8 The experiment we have just described is a very old one. M. V. Sircoulon has told us that it was described at length in the works of Rabelais. The following remarks are in “Pantagruel,” book II., chap. xvii.

“Panuræ then took two glasses of the same size, filled them with water, and put one on one stool, and the other on another, about five feet apart, and placed the staff of a javelin about five-and-a-half feet long across, so that the ends of the staff just touched the brim of the glasses. That done, he took a stout piece of wood, and said to the others: “Gentlemen, this is how we shall conquer our enemies; for in the same way that I shall break this staff between these two glasses, without the glasses being broken or injured, or spilling a single drop of water, so shall we break the head of our Dipsodes, without any injury to ourselves, and without getting wounded. But that you may not think there is magic in it, you, Eusthenes, strike with this stick as hard as you can in the centre.” This Eusthenes did, and the staff broke in two pieces, without a drop of water being spilt.

9 The curved surface of a column of liquid is termed a “meniscus,” from the Greek word meniskos, meaning “a little lens.”
10 Traité de Physique, Paris 1874.
11 Traité d’optique Physiologique. French translation by MM. Javal and Klein.
12 From praxis, action, and skopein, to show.
13 This interesting experiment, which we have exactly verified, was described to us by Professor Waldner, and M. A. Keppler.
14 Ganot: Eléments de Physique.
15 Encly. Metrop.
16 “Treatise on Electricity and Magnetism.”
17 Sabine: “The Electric Telegraph.”
18 We are indebted for many facts respecting Mr. Edison’s light in this chapter to a paper by Mr. Upton.
19 It is the same with a number of other common products, such as clay, sandstone, etc., the composition of which chemistry has revealed. Argil, or clay, slate, and schist all contain a metal—aluminium, which has become most valuable for industrial purposes. Stones for building are composed of a metal combined with carbon and oxygen—calcium; sandstone is composed of silicium, a metallic body united with oxygen; and sulphate of magnesia, which enters into the composition of a purgative drink, also contains a metal—magnesium.
20 These substances must be finely powdered and thoroughly mixed.
21 Requires oxy-hydrogen blow-pipe.
22 Cyanogen, ethyl, and cacodyl, are compound radicals.
23 A crystal should be held so that one of its axes is vertical to the spectator. This axis is termed the principal axis, and when there is inequality the longest axis is the principal.
24 See “Strontium” in Chemistry.
25 He was obliged to recant before the Inquisition, and to repudiate his researches. He was released on the condition of observing silence upon the theory he had supported, but again obliged to recant.
26 The bright part of the sun.
27 Mr. Burnham has lately given a list of two hundred and fifty-one new double stars, and in the Astronomical Society’s proceedings there is a list of ten thousand.
28 It might reach 14,000,000 of miles at a maximum.
29 “Physical Causes of Change of Climate,” _Phil. Mag._, 1864.
30 See Dawkins’ “Early Man in Britain.”
31 From Artois, where the first European well of this kind existed.
32 Those who wish to study the subject fully should read “Corals and Coral Reefs,” by the late Charles Darwin, and Dana’s “Coral Islands.”
33 See “Molecular Physics” (Tyndall).
34 “Fulgarites” are composed of melted quartz, and on Mount Ararat many have been found which give a character to the formation of the lesser Ararat.
35 Dr. Carpenter.
36 Respecting artificial colouring of flowers, see page 329.
37 Carpenter on the Microscope.
38 Huxley. “Classification of Animals.”
39 That the presence of millions of such ova in the air should not be detected, will appear very natural indeed, if we reflect that the animalcules are only 1/1500 to 1/2000 part of a line in diameter, and that the ova are a thousand times smaller.
40 Hercules conquered the “Hydra,” which is represented in mythology as capable of reproducing two heads for each one cut off by the warrior.
41 From “La Nature.” Notice of M. Ch. Boutemps.
42 Kampulos, a curve; metron, measure.

Leaf Shapes from the illustration on page 672

Lanceolate (Privet).
Ovate (Fuchsia fulgens).
Oblong (Primrose).
Cordate (White Bryony).
Palmate (vine).

II. Depending on Margin and Arrangement.

Serrate (Rose).
Biserrate (Elm).
Crenate (Betony).
Entire (Lilac).
Digitate (Lupin).
Pinnate (Vetch).
Bipinnate (Acacia).
Pinnatifid (Crepis).
Ternate (Clover).
Biternate (Columbine).

III. Depending on Point.

Obtuse (Dock).
Mucronate (Holly).
Retuce (Snowball).
Emarginate (Bladder Senna).

Moon Features
Table of the features illustrated in Figure 565, page 514

A Mare Crisium.
B Palus Somnii.
C Mare Serenitatis.
D Mare Tranquillitatis.
E Mare Fœcunditatis.
F Mare Nectaris.
G Sinus Medii.
H Mare Vaporum.
I Lacus Mortis.
J Mare Frigoris.
K Mare Imbrium.
L Oceanus Procellarum.
M Mare Humorum.
N Mare Nubium.
O Sinus Iridium.

a Apennine Mts.
b Caucasus.
c Carpathians.
d Pyrenees.
e Altai Mts.
f Riphaen Mts.
g Doerfel Mts.
h Leibnitz Mts.
i Corderillas.
j D’Alembert Mts.
k Taurus Mts.
l Hæmus Mts.
m Alps.

1 Clavius.
2 Maginus.
3 Maurolycus.
4 Stöfler.
5 Tycho.
6 Longomontanus.
7 Wilhelm I.
8 Schiller.
9 Schickhardt.
10 Hainzel.
11 Furnerius.
12 Metius.
13 Fabricius.
14 Riccius.
15 Piccolomini.
16 Zagut.
17 Apianus.
18 Walter.
19 Hell.
20 Pitatus.
21 Hesiodus.
22 Capuanus.
23 Ramsden.
24 Vieta.
25 Peravius.
25 Vendelinus.
27 Langrenus.
28 Fracastorius.
29 Theophilus.
30 Cyrillus.
31 Catharina.
32 Sacrobosco.
33 Almanon.
34 Albufeda.
35 Albategnius.
36 Hipparchus.
37 Ptolemy.
38 Alphonsus.
39 Purbach.
40 Regiomontanus.
41 Thebit.
42 Arzachel.
43 Bullialdus.
44 Lalande.
45 Mösting.
46 Herschel.
47 Gassendi.
48 Mersenius.
49 Sirsalis.
50 Grimaldi.
51 Riccioli.
52 Hevelius.
53 Condorcet.
54 Taruntius.
55 Proclus.
56 Cleomedes.
57 Romer.
58 Posidonius.
59 Plinius.
60 Julius Cæsar.
61 Manilius.
62 Godin.
63 Agrippa.
64 Triesnecker.
65 Bode.
66 Gambart.
67 Eratosthenes.
68 Copernicus.
69 Reinhold.
70 Landsberg.
71 Encke.
72 Kepler.
73 Marius.
74 Archimedes.
75 Timocharis.
76 Euler.
77 Aristarchus.
78 Herodotus.
79 Struve.
80 Messala.
81 Mare Humboldtanius.
82 Atlas.
83 Hercules.
84 Endymion.
85 Eudoxus.
86 Aristoteles.
87 Linne.
88 Autolycus.
89 Aristillus.
90 Cassini.
91 Plato.
92 Helicon.
93 Pythagoras.

Transcriber's Notes

Obvious typographical errors have been silently corrected but variations in hyphenation and all other spelling and punctuation remains unchanged.

The following corrections have been made:

Réamur has been corrected to Réaumur throughout.

Page 94 “There are seven primary colours in the sunlight, which is white. These can be divided or “dispersed,” and the shortest rays of the spectrum are found to be red, the longest violet.” has been corrected.

Page 109. “If, for instance, we place on a disc covered with blue and red sectors of equal size, a black disc, of which the sectors are alternately filled in or empty, the disc, as it turns round, will appear blue if the black sectors of the upper disc exactly cover the [red] sectors of the lower disc; and it appears red, if, on the contrary, the blue sectors are covered with the black;” [red] has been added.

Page 238. The footnote Monvel’s “Course of Physics.” appears, but there is no reference to it in the text.

Page 533. The time of revolution of Saturn’s Moons was given in d. h. sec., this has been corrected to d. h. min.