ON THE HEAT PRODUCED BY FRICTION. $J 



to water. On the bottom, namely in the end of the block, 

 and perpendicular to its fibres, was fixed a small steel anvil 

 of 3 cent. 25 mil. On two opposite sides, level with the an- 

 vil, were two leather boxes, by means of which a wire could 

 traverse the box, without letting out the water. This wire, 

 part of which rested on the anvil, was subjected to strong 

 compression by means of a prismatic stamper of steel, which 

 descended through the cover of the little box, and moved 

 in a groove, that directed its lower extremity to the anvil. 

 This stamper, driven by hard strokes with a hammer, trans- 

 mitted to the wire, on which it rested, the blows it received, 

 and compressed it. The hammer I employed weighed 2kil. 

 [4 lb. 6| oz.] At every stroke the wire was advanced two 

 thirds of the breadth of the anvil. The metal subjected to 

 experiment was an iron wire one third of a line in diameter, 

 and of the weight of 366 grains [300 grs Eng.]. Com- 

 pressed throughout by the mechanism I have described, it 

 formed a band a little more than a line broad, and its length 

 was increased; but its specific gravity had acquired no per- 

 ceptible increase. The temperature of the water employed 

 to collect the caloric evolved by this condensation rose only 

 2° [3 -6°]. As my balance detects a variation of less than 

 half a grain, a change in the density, less than would pro- 

 duce a difference of half a grain in the specific gravity of 

 366 grains of iron wire weighed in water, extricated a quan- 

 tity of heat that raised the temperature of a cubic decime- 

 ter of water one degree, and consequently would have 

 melted more than an eighteenth part of ice. 



If the experiments I have described had not all the sue- Friction pro- 

 cess I expected to determine the cause, that prodnces the ^ cesanaston " 



• i P . • o , lshingquan- 



heat extricated in the friction of substances, they appear to thy of heat, 



me not destitute of utility. They not only confirm the ex- 

 periments of count Rumford concerning the astonishing 

 quantity of heat produced by friction, but they prove (al- 

 lowing for the irregularities unavoidable in experiments of 

 this sort), that this quantity of heat is modified by the na- and thisisnei- 



ture of the substances rubbed ; that it is not in the ratio of ther f n tl ! he ra " 



iio oi mc sur» 



the surfaces, for equal surfaces have given unequal quanti- face rubbed, 



ties ; and that it is not in the ratio of the number of parti- 'I 16 de ? sity of 



ro i tne substance, 



cles rubbed oft, or ot the density; for lead, the density of northequanti- 



which l * abraded ' 



