9 



cool-headed insurance men and cautious farmers in mutual insurance companies, 

 where the assessment is in direct proportion to the losses incurred. This is the 

 protective value of lightning rods reduced to dollars and cents in insurance rates. 

 Insurance men the world over cannot ignore the experience of the Michigan 

 Companies. Farmers the world over should profit from the lessons taught by the 

 Michigan farmers. 



Being now assured that lightning rods are of high protective value, our next 

 logical enquiry would be: "When is a building properly rodded?" Before one 

 can appreciate some of the directions to be given for rodding a building he must 

 have at least a limited knowledge of electricity and its laws, and this we shall 

 now proceed to acquire, leaving directions for rodding to come later on page 24. 



Discovert op Electricity, 



If a small piece of cheap scribbling paper, after being warmed to dry it, be 

 rubbed briskly upon the coat sleeve for a few moments and then placed against 



Fig. 1. — Paper rubbed briskly on 

 coat sleeve adheres to hand. Paper 

 is electrified by friction. 



Fig. 2. — Pith balls suspended by 

 thread to be used in experiments. 



silk 



the window pane, it adheres to the glass, or it will adhere to the hand. (Fig. 1.) 

 Another piece not rubbed, does not adhere to glass or hand. Hence tjie rubbing has 

 produced some new property in the paper. The first experiment of this kind was 

 performed by Thales, an ancient Greek, in the year 640 B.C. While walking along 

 the seashore he picked up a piece of amber. In order to burnish it he rubbed it 

 briskly upon his garments, and in some way or other discovered that after the rub- 

 bing the amber had the property of attracting light substances, such as dry leaves, 

 twigs and chaff to itself. The Greek word for amber is dectron, and hence 

 this new property first discovered in the amber has come to be known as elec- 

 tricity. The paper in being rubbed upon the coat sleeve is said to have become 

 electrified. In the year 70 A.D. electricity is again mentioned in history, but no 

 real progress was made until the year 1600 A.D. Then Dr. Gilbert, a famous Eng- 

 lish scientist, discovered that all substances when properly manipulated could be 

 electrified by friction just as the amber waa. 



