of the Cylinder Electrical Machine. 255 



jar, without its weight or bulk being increased. If any means 

 could be discovered of coating metal with glass or enamel, 

 and vice versa, a single jar might be made to have the power of 

 an ordinary battery ; and until something like this has been ac- 

 complished, the use of powerful batteries must remain in the 

 hands of the opulent, and those of scientific bodies, lhaveheard 

 of a battery of plates in the shape of a quarto volume; but 

 however well this shape may answer on account of its porta- 

 bility, it is not well adapted for the purpose, as the insulating 

 edge must go all round ; but if we bend one of these plates 

 into the shape of a cylinder, and put a bottom in, there is but 

 one edge left to keep clean, and the other three are added to 

 the coated surface, independently of the bottom, besides being 

 of a much more convenient shape. A metal jar maybe made 

 and coated with sealing-wax, and the latter with tin-foil ; but 

 how far this method could be carried by inverted jars remains 

 to be tried. 



The first Henley's universal discharger that I made had 

 two insulated wires, in the usual way; but if I had been asked 

 the use of the second insulation, I should have been at a loss 

 what to answer, as a jointed wire answers every purpose, 

 and is much less in the way. The lower plate of the electro- 

 phorus is formed with a smooth round edge : it is filled with 

 shell-lac. It forms the table of the universal discharger : 

 when inverted and set on a drinking-glass, and a chain hooked 

 on, it forms the lower plate for the dancing figures, &c. ; 

 without the chain, it forms the insulated stand. The I'esinous 

 side will do to form Professor Lichtenberg's figures upon. 

 The glass itself will form a jar with moveable coatings, and 

 will do for the dancing balls, &c. 



What is called the electrical pistol is a mortar or howitzer, 

 which has to be filled with inflammable air, and fired by a se- 

 parate Leyden jar : a real electrical pistol may be easily made. 

 Take a pistol-stock and fix an ivory barrel on it with an in- 

 terrupted circuit in it : then bore a hole through the stock. 

 Take one of the smallest Leyden phials, and fit a brass tube 

 as an outside coating ; solder a wire to the coating, insert it 

 in the hole and bend the end of the wire to form the trig- 

 ger ; then put a cork with a particle of fulminating silver into 

 the barrel ; charge the phial, and fire it at a mark in any part 

 of the room ; which may be done twenty times whilst the other 

 is getting ready. 



Another advantage (independent of the cheapness attend- 

 ing coated green glass) is that the stools and chairs would 

 look like common ones ; I have seen nervous patients thrown 

 into a state of feverish excitement only by being placed on a 



glass 



