[9] These three pictures are drawn, by permission, from photographic illustrations by Mr. Jennings in Journal of the Franklin Institute, vol. 133 (1892).
Fig. 131. Horizontal discharge of lightning.
Fig. 132. Meandering discharge.
Fig. 133. Tree-form discharge.
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.
METAL ROOFS
It has been noticed that metal roofs protect buildings even when no lightning rods are used, especially if there are tin or iron water pipes running to the ground. Even steam and gas pipes are good if connected with the roof. Tin and copper roofs are not so common in the country as in the city, and this is one of the many reasons why city houses are less frequently struck by lightning than country ones. Copper roofs are not used now as they once were on account of the great expense; but from the electrical standpoint they are an excellent protection to a house in a thunder storm. The writer has noticed in a room in a city house, in which steam heat is used, that the lightning will come in and down on the steam pipes without doing any harm. If one will go into a telegraph station during a storm he will frequently notice the discharges of lightning which take place through devices provided for the purpose, and this without the least fire risk. This is an illustration of the fact that, if properly provided for, the dangerous element can be largely eliminated from a lightning discharge.