

CHEMISTRY. 167 



its condensation, communicate heat sufficient to boil 

 a large quantity of water. 



A given quantity of steam will produce, by its 

 condensation, a much greater elevation of tempera- 

 ture, than the same quantity of boiling water. 



Boiled Potatoes. 



One per cent, to the bulk of water is put into the 

 boiler of the steam-engine, to prevent the cohesion of 

 the precipitated calcareous salts, (selenite or carbo- 

 nate of lime). The boiler is emptied once a month, 

 and new potatoes added. This has been long prac- 

 tised in England, but only recently in France. 



Heat. 



Nothing is known of the nature of heat, or of ca- 

 loric, its cause. Count Rumford has clearly proved 

 that it has no weight. A phial of spirits of wine and 

 one of water remained in equilibrium after the latter 

 was frozen, although it thereby lost as much caloric 

 as would have brought to a white heat the same 

 weight of gold. 



It is generally admitted, that the atoms of caloric 

 are attracted by every other substance, while they 

 mutually repel each other. 



Friction. 



Sir H. Davy melted two pieces of ice by their 

 mutual friction, in a room cooled below the freezing 

 temperature. 



Newton's Subtle Fluid. 



That a subtle fluid existed, and was diffused 

 through those spaces from which air was exhausted, 

 appeared evident to Sir Isaac Newton, from many 



