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THE POPULAR SCIENCE MONTHLY. 



of induction gives you over these wonderful and complicated phenom- 

 ena. By those principles the various facts of our science are bound 

 together to an organic whole. But we have not yet exhausted the 

 fruitfulness of this principle. 



Consider the following problem. Usually we allow the electricity 

 of the outer coating to escape to the earth. Suppose we try to utilize 

 it. Place, then, your jar upon vulcanized India-rubber, and connect 

 its outer coating by a wire with the knob or inner coating of a second 

 jar. What will occur when the first jar is charged ? Why, the 

 second one will be charged also by the electricity which has escaped 

 from the outer coating of the first. And suppose you connect the 

 outer coating of the second insulated jar with the inner coating of a 

 third; what occurs? The third jar will obviously be charged with 

 the electricity repelled from the outer coating of the second. Of 

 course, we need not stop here. We may have a long series of insu- 

 lated jars, the outer coating of each being connected with the inner 

 coating of the next succeeding one. Connect the outer coating of the 

 last jar with the earth, and charge the first jar. You charge thereby 

 the entire Series of jars. In this simple way you master practically, 

 and grasp the theory of the celebrated " cascade battery'''' of Frank- 

 lin, represented in Fig. 26, with coated glass tumblers, J, J5, C, D t 



Fig. 26. 



and so on. You must see that, before making the experiment, you 

 could really have predicted what would occur. This power of pre- 

 vision is one of the most striking characteristics of science. 



Sec. 19. Novel Ley den- Jars of the Simplest Form, But, possessed 

 of its principles, we can reduce the Leyden-jar to a far simpler form 

 than any hitherto dealt w r ith. Spread a sheet of tin-foil smoothly 

 upon a table, and lay upon the foil a pane of glass, somewhat 

 smaller than the foil in size. Remember that the glass, as usual, must 

 be dry. Stick on to the glass by sealing-wax two loops of narrow 

 silk ribbon, by which the pane may be lifted; and then lay smoothly 

 upon the glass a second sheet of tin-foil, less than the pane in size. 



