OF GASEOUS EXPANSION AND CONTRACTION. Ill 



of ponderable matter is in proportion to their size, 

 ceteris paribus. For example, the atoms of hy- 

 drogen are smaller, and contain a larger amount 

 of caloric around them, than those of any other 

 gas ; the consequence of which is that its elastic 

 force is such, that no mechanical pressure hitherto 

 employed has been sufficient to condense it into 

 the liquid form.* And it was found by Perkins, 

 that atmospheric air (which is composed of oxy- 

 gen and nitrogen in a state of mechanical mix- 

 ture) may be submitted to a pressure equal to 

 1200 atmospheres, without being perfectly con- 

 densed into the liquid form. (Philosophical 

 Transactions, 1826.) 



But when 3 volumes of hydrogen unite chemi- 

 cally with 1 of nitrogen, they contract into 2 



* Under the pressure of the atmosphere, and at the tem- 

 perature of 60, hydrogen is 15,480 times lighter than water, the 

 pores of which are 40 times larger than its solid particles, accord- 

 ing to Newton. It is therefore evident, that the pores of hydrogen 

 exceed the diameters of its particles several thousand times, and, 

 perhaps, to the same extent, that the spaces between the different 

 planets exceed their mean diameters. What, then, is the cause of 

 the stupendous force by which the particles of hydrogen are kept 

 at such comparatively great distances from one another ? Is it 

 some virtue, property, or condition termed polarity? Or is it 

 owing to the existence of certain hypothetical immaterial spheres 

 of repulsion around its particles ? Is it possible that masses, and 

 the atoms of which they are composed, are capable of acting upon 

 each other at comparatively great distances without an intervening 

 medium ? That the volume of gaseous bodies is augmented by 

 every addition of caloric, has been proved by the experiments of 

 Gay-Lussac, who found that 1000 cubic inches of common air 

 were expanded to 1 375 cubic inches by raising its temperature from 

 32 to 2 1 2. It was further ascertained by Dulong and Petit, that 



