214 A 7iew Theory of Galvanism. 



small pieces in a flat hook of sheet iron. But the best mode of 

 application is by means of a trav made by doubling a slip of 

 sheet iron at the ends, and leaving a receptacle in the centre, in 

 which the potash may be placed covered with filings. This tray 

 being substituted for the connecting wire, as soon as the immer- 

 sion of the apparatus causes the metal to burn, the rose-coloured 

 flame appears; and if the residuum left in the sheet iron be after- 

 wards thrown into water, an effervescence sometimes ensues. 



I have ascertained that an iron heated to combustion, by a 

 blacksmith's forge tire, will cause the decomposition of the hy- 

 drat of potash. 



The dimensions of the Calorimotor may be much reduced 

 without proportionably diminishing the effect. I have one of 

 sixty plates within a cubic foot, which burns off No. 16, iron 

 wire. A good workman could get 120 plates of a foot square 

 •within a hollow cube of a size no larger. — But the inflammation 

 of the hydrogen which gives so m.uch splendour to the experi- 

 ment, can only be exhibited advantageously on a large scale. 



Explanation of the Plate (III). — A a, fig. 1st, two cubical ves- 

 sels, 20 inches square, inside, b b b b a frame of wood containing 

 20 sheets of copper, and 20 sheets of zinc, alternating with each 

 other, and about half an inch apart. T T 1 1 masses of tin cast 

 over the protruding edges of the sheets which are to communi- 

 cate with each other. Fig. 2. represents the mode in which the 

 junction between the various sheets and tin masses is effected. 

 Between the letters z z, the zinc only is in contact with the tin 

 ~ asses. Between c c, the copper alone touches. It may be ob- 

 served, that, at the back of the frame, ten sheets of copper between 

 c c, and ten sheets of zinc between z z, are made to communi- 

 cate by a common mass oPtin extending the whole length of the 

 frame, between T T: but in front, as in fig. 1, there is an inter- 

 stice between the mass of tin connecting the ten copper sheets, 

 and that connecting the ten zinc sheets. The screw forceps, 

 appertaining to each of the tin masses, may be seen on either 

 side of the interstice; and likewise a wire for ignition held be- 

 tween them. The application of the rope, pulley, and weights 

 is obvious. The swivel at S permits the frame to be swung 

 round and lowered into water in the vessel a, to wash off the 

 acid, which, after immersion in the other vessel, might continue 

 to act on the sheets, encrusting them with oxide. Between p p 

 there is a wooden partition which is not necessary, though it may 

 be beneficial. 



Fig. 3. represents an apparatus alluded to p. 211. — It consists 

 of a couronne des tasses, reduced to a form no less compact than 



that 



