i62 CLASSICS OF MODERN SCIENCE 



that this operation took place in a similar manner in all parts of the 



cylinder. 



"As a consequence of this decrease of volume, an amount of caloric 

 was given out equal to that which would have caused a similar increase 

 of volume, on the supposition, that is, that the specific heat of the metal 

 does not change through this range of the scale of the thermometer, and 

 that the expansions are equal; and this, considering the range of tem- 

 peratures and the consequent expansions, is probably not far from the 

 truth. The entire amount of heat disengaged would have raised the 

 cylinder to about i8o ° of Reaumur's scale ; and if the expansion of 

 brass by heat is equal to that of iron, which has been found to be 

 1-75000 for each degree of the thermometer, the 180 degrees would have 

 caused an expansion of 18-75000 in each direction, and the decrease of 

 volume must have brought about the same degree of heat if we sup- 

 pose that the pressure stood in equal relation to this expansion. 



"Now there is a change, and sometimes a very considerable one, 

 wrought in the specific gravity of a metal, by percussion, by the action 

 of a fly-wheel, or by the compression of a wire-drawing machine. It 

 appears, for example, that the specific gravity of platina and of iron, 

 on being forged, is thus increased by a twentieth part. 



"Hence it appears that the experiment of Count Rumford is far 

 from explaining satisfactorily a property which is well known, and 

 called in question by no one. 



"It is easy, it is true, to arrange side by side in an imposing manner 

 the phenomena of heat; if, however, you were to say to one who has 

 little or no knowledge of chemical speculations, 'Count Rumford's cylin- 

 der has, in the course of two hours, by means of a violent friction, 

 afforded all the heat required to dissolve in water, without changing its 

 temperature, 15 kilogrammes of ice, or as much as 2 hectogrammes 

 (6y2 ounces) of oxygen would require [sici in its combination with 

 phosphorus,' I do not know at which of these phenomena he would be 

 most astonished. 



"The slight changes which can take place in the amount of com- 

 bined caloric have so inconsiderable an influence on the capacity for 

 work of the caloric within the narrow limits of the thermometric scale, 

 that it cannot be computed. Moreover, we have not, as yet, adequate 

 data for determining the nature of the changes in this respect which 

 take place in a solid body in consequence of the particular condition of 

 condensation into which it has been brought by means of certain me- 

 chanical force, and by degrees of heat differing greatly from each other. 



"Besides, Rumford, in the experiment to determine the specific heat 

 of the filings of bell-metal thus obtained, heated them to the temperature 



