TABLE OF FAVRE AND SILBERMANN. 83 



snow-flakes descending so softly as not to break their 

 fragile spangles. Yet to produce from aeriform gases a 

 quantity of that tender material, which a child might lift, 

 demands an exertion of energy competent to gather up 

 the shattered blocks of the largest stone-avalanches I 

 have ever seen, and project them to twice the height 

 from which they fell." l 



Favre and Silbermann have applied the British 

 thermal unit (seven hundred and seventy -two 

 foot-pounds), to measure the quantity of heat im- 

 parted to bodies to change their component par- 

 ticles from solid to liquid states, and from liquid 

 to aeriform states, in carrying out the dynamic 

 theory of heat as " a mode of motion." They give 

 the following calculation of the extent of action 

 developed by " the clashing of one pound of mole- 

 cules of hydrogen with eight pounds of molecules 

 of oxygen, in the process of combustion, producing 

 nine pounds of water." 



DYNAMIC ACTION OF MOLECULES. 



Another chemist explains the clashings and en- 

 counters of molecules in the following words : 



1 Heat considered as a Mode of Motion, Lecture V. By John Tyn- 

 dall, F. R. S. 



