■ 



W 



ivi Life and writings of Count Humford. 



I 



quires by repeated firinSjV serves to increase the strength of the 

 powder. He tried the effect of an admixture of various substan- 

 ces with gunpowder^ to increase its force ; such as carbonate of 

 potash^ sal ammoniac^ brass filings, alcohol and water. These 

 were all, however, found to diminish rather than increase the ef- 

 feet of the explosion. He calculated the force of fired gunpowder 

 to be equal to fifty thousand atmospheres, a force much exceeding 

 that ascribed to it by previous calculators, and which has since 

 been thought to exceed the probable truth. 



Count E^umford made many experiments on the conducting 

 power of different substances for heat, with a view to their practi- 

 cal application in clothing, building, &c. It is, however, impos- 

 sible to subject the different clothing stuffs, such as wool, silk, 

 fur, down, &c. to very accurate experimental tests, since their 

 conducting power must always vary in proportion to the closeness 

 of their fabric. Thus a loose flannel will always be a worse con- 

 ductor of heat than a compact or glazed cloth made of the same 

 material in equal quantity. The general conclusions of the Count, 

 however, are correct, that cmteris paribus, the finer the fibre is, 

 the worse conductor will the stuff be which is composed of it. 

 The non-conducting power of these substances is properly at- 

 tributed to the air retained among the fibres by attraction of the 

 capillary kind. The greater is the amount of air made station- 

 ary by this attraction, the better non-conductor will the sub- 



i 



stance become. 



Being employed to superintend the boring of cannon at Mu- 

 nich, he availed himself of the occasion for experiments on the 

 heat excited by friction. Having confined the end of the gun, 

 while boring, in a box filled with water, he observed the change 



