ELECTRICAL APPARATUS. 321 



which touches the inner coating of the tube, and this tube 

 being so small, the shocks which will pass will be less 

 energetic than those given by the larger bottle, and will 

 altogether have a different character. They are, indeed, 

 intermediate in effect, between sparks and shocks, and are 

 called vibrations. 



Fig. 377. 



Fig. 377, as above, shows the usual method of adminis- 

 tering a shock through a number of persons at once, sup- 

 posing we have not the apparatus above described, and that 

 we desire only amusement. The phial on the table is 

 charged ; a chain connects its outside to the first person, he 

 by joining hands to the second, and so on to the end ; the 

 last person touching the knob of the phial with a wire and 

 ball. If the persons shocked turn their backs to the phial, 

 the shock will reach them more unexpectedly 



Hydro- Electrical Machine. The production of electricity 

 by the passage of steam through a small jet, was unknown 

 till 1840. Professor Faraday concludes that it is the effect 

 of the friction of globules of water against the sides of the 

 opening, urged forward by the rapid passage of the steam ; 

 the effect of this is to render the steam or water positive, 

 and the pipes from which it issues negative. 



In the following cut (Fig. 378, next page), A, A, A, A, A, A, 

 are six green glass supports, three feet long ; B is a cylindri- 

 cal tubular boiler of rolled iron-plate, f inch thick ; its extreme 



