422 Hart's Calorimotor. 



the zinc plates. On each of the approaching terminations of 

 the connecting tin strata was soldered a kind of forceps, 

 formed of a bent piece of sheet brass, furnished with a screw 

 for pressing the jaws together. The distance between the 

 different forceps was about two inches. The advantage of a 

 very close contact was made very evident by the action of the 

 screws ; the relaxation or increase of pressure on the con- 

 necting wire by turning them being productive of a corres- 

 pondent change in the intensity of ignition . 



It now remains to state, that by means of iron ignited in 

 this apparatus, a fixed alkali may be decomposed extempo- 

 raneously.* If a connecting iron wire, while in combustion, 

 be touched by the hydrate of potash, the evolution of potas- 

 sium is demonstrated by a rose-coloured flame. The alkali 

 may be applied to the wire in small pieces in a flat hook of 

 sheet iron. But the best mode of application is by means of a 

 tray 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 immersion of the 

 apparatus causes the metal to burn, the rose-coloured flame 

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

 ward thrown into water, an effervescence sometimes ensues. 



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

 blacksmith's forge fire, will cause the decomposition of the 

 hydrate 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 inflamma- 

 tion of the hydrogen which gives so much splendour to the 

 experiment, can only be exhibited advantageously on a large 

 scale. 



* This evidently dift'ers from the common mode of decomposing the fixed alka- 

 lies by galvanism : there the effect depends on electrical attractions and repul- 

 sions — here on the chemical agency of ignited iron produced extemporaneously in 

 the galvanic circuit : ihis mode of operating appears to be new. Editor. 



