A flash of lightning is one of the most feared of nature’s manifestations of power; and yet by the use of proper precautions its ability to injure persons and property can be lessened greatly. Speculations as to the nature of lightning were vague until Benjamin Franklin boldly sent a kite into the teeth of a storm and tapped the accumulated electricity in the cloud to charge one of his storage jars. He connected the cloud with his jar by a wire made of a material which he knew would conduct the electrical charge, and at the same time he took the precaution not to hold the end of this wire himself. He introduced between the end of the wire and his hand a piece of silk cord, which is a non-conductor of electricity. Had he taken hold of the end of the wire, the charge would have passed through him with probably fatal results.

What is lightning? One naturally inquires for the reason of this storage of electrical energy in the clouds. The explanation is not forthcoming—at least there is none which is entirely satisfactory—but the facts are well known. The mass of water-vapor which forms the clouds becomes electrically charged just as a rubber comb does when rubbed on the hair on a dry day, or as an ebonite ruler does when rubbed on a cat-skin. Perhaps by contact with the air, which is in motion, the particles of water become charged, and by the union of multitudes of these the clouds are charged to a tremendous pressure. Lightning can be produced artificially on a small scale by means of electric machines, and the results of study of these artificial discharges have been to show the following facts: The air is not a conductor of electricity, but when the electrical pressure between two points becomes sufficiently great the electric charge jumps suddenly between the two points at which the pressure exists. It punctures a hole for itself through the air. Lightning is the result. This discharge is very violent, and it is accompanied by a strong smell of ozone, which is only very strong oxygen. If one were to examine the points of the electric machine between which the discharge took place, they might be found either hot or cold, depending upon their size and the material of which they were made. Some materials offer more resistance to the passage of the electric charge than others, and when a considerable resistance is offered, heat is produced in appreciable amounts at the places at which the resistance is met. The application of this principle will be seen when the effects of real lightning are considered.

In Figs. 131, 132, and 133 are shown lightning flashes taken by Mr. W. N. Jennings.[9] These flashes are so soon over that without the aid of the sensitive photographic plate it would be impossible to study them. It will be noticed that the path of the charge is not straight, but quite irregular; this path being that in which there is the least resistance to the passage of the electricity. One strange phenomenon which is brought out clearly in the pictures is that the discharge very frequently divides into several branches. This is because it finds easy paths in several directions and divides into smaller discharges, thus finally disappearing.

Protection from lightning.—Having noticed briefly something of the nature of lightning, the next point to be considered is its control, so that the dangerous effects of a sudden discharge may be avoided. It has long been known that by repeating Franklin’s experiment and connecting the clouds with the earth, dangerous flashes of lightning can be avoided to some extent; and this fact has given rise to much swindling on the part of the “lightning-rod man,” who has frequently imposed on the people through their fear of the results of lightning bolts. Any person of average intelligence, with the knowledge of a few simple principles, can put up a rod himself for the protection of his barn or dwelling at a very reasonable expense.