4~ Modns of increajing the Quantities of Heat 



were moiftened with a folution of common fait. If the 

 cloths be foaked in acids, the refult, as every one knows, 

 will be very different ; the pile will then act as powerfully 

 even in vacuo as in atmofpheric air. 



An anonymous correipondent, in the lad number of the 

 Philofophical Magazine, notices the increafed action of the 

 pile by acids; but becaufe he finds that the alkalies, particu- 

 larly pure ammonia, alfo increafe its action molt powerfully, 

 infers, that the fluid excited in the pile does not arife from 

 the action of acids, or from any combination of oxygen with 

 ■the metals. Before making fuch an inference, he ought to 

 have tried his pile in fuch circum (lances as would have pre- 

 cluded the poflibility of oxygen having accefs to it. In vacuo 

 his pile would have fpeedily ceafed to act, even with folutions 

 of alkali interpoied between the pairs of plates. He ought 

 alfo to have examined the fiate of the refidual water in the 

 two glaffes, connected by means of a fyphon, before he pro- 

 ceeded to overturn the Lavoifierian fyftem from the circum- 

 flance of oxygen gas being produced in the une glafs and 

 hydrogen gas in the other. 



The laft paragraph in his paper is equally inconclufive, 

 where he would infer, becaufe an electrometer gives figns of 

 negative electricity when a drop of water is let fall upon a 

 piece of red-hot iron placed upon it, that therefore poiitive 

 electricity and water form hydrogen air. The pre fence of 

 hydrogen is not necefTary to the electrometer indicating ne- 

 gative electricity ; if the water be converted into vapour, the 

 effect is produced : indeed, the vapour of any kind of liquid 

 produces the negative itate. 



VII. Obfervathns on the Means of increafing the Quantities 

 of Heat obtained hi the Combuflion of Fuel. By Count 

 Rum ford*. 



JLT is a fact which has been long known, that clays, and 

 feveral other incombuftiblc fubftances, when mixed with 

 fea-coal, in certain proportions, caufe the coal to give out 

 more heat in its com bullion than it can be made to produce 

 when it is burnt pure or unmixed ; but the caufe of this in- 

 creafe of heat does not appear to have been yet inveftigated 

 with that attention which fo extraordinary and important a 

 circumftance ftems to demand. 



Daily experience teaches us, that all bodies— thofe which 



* From the Journals cf the Royal Injiitutlon of Great Britain. 



are 



