2O8 SCIENTIFIC RECREATIONS. 



and coated with tinfoil. The ends should be rounded like " knobs." Stick 

 pins in to collect the electricity (and it will be readily obtained). The cushion 

 should of course be well smeared with amalgam. From this, as well as from 

 the glass-plate machine, the " positive " electricity can be drawn off and 

 stored in a Leyden jar, and then discharged by the " discharging rod," which 

 is represented on the cut. It may have one or two handles, and one knob 

 is placed outside the jar, the other near the ball surmounting it. The glass 



Fig. 213. Cylinder machine. 



being a non-conductor saves the operator, and some long sparks and loud 

 reports may be obtained. 



The Electric Machine is always assumed to give off positive electricity. 



Sir William Armstrong's Electric Machine is a mode of obtaining 

 electricity by moist steam. The design is Armstrong's, and Professor Faraday 

 subsequently went into all the conditions to produce the " fluid " by the 

 friction of steam. The machine was something like a small boiler supported 

 on glass legs. A row of nozzles was fixed upon the escape pipe so as to 

 create a great velocity and friction in the escaping steam. Round the nozzles 

 was a box of cold water, for that fluid was found necessary for the production 



Fig. 214. Discharging rod. 



of electricity as demonstrated by Professor Faraday. The steam rushed 

 against a row of points attached to the prime conductor of an electric 

 machine, and the electricity of the steam was thus given off to the conductor. 

 There are many other forms of electric machines, but it will serve no purpose 

 to detail them. 



The Electric Battery (see fig. 206) is formed by a collection of Leyden 

 jars. The inside and outside coatings are connected in a box divided into 

 partitions lined with tinfoil. The rods of the jars are also connected, as in 

 the illustration, by brass rods, and when this battery is charged people should 

 be careful how they handle it, for a shock may be produced which would 



