CHEMICAL EFFECTS OF DECREASmG HEAT. 41 



tliroiigbout. Without entering into qualifications for 

 wliich we lack space, we believe no chemist will deny it to 

 be a general law of these inorganic combinations that, 

 other things equal^ the stability decreases as the complexify 

 increases. 



And then when we pass to the compounds of organic 

 chemistry, we find this general law still further exemplified : 

 we find much greater complexity and much less stability. 

 An atom of albumen, for instance, consists of 482 ultimate 

 atoms of five difierent kinds. Fibrine, still more intricate 

 in constitution, contains in each atom, 298 atoms of carbon, 

 40 of nitrogen, 2 of sulphur, 228 of hydrogen, and 92 of 

 oxygen — in ail, 660 atoms ; or, more strictly speaking — 

 equivalents. And these two substances are so unstable as 

 to decompose at quite ordinary temperatures ; as that to 

 which the outside of a joint of roast meat is exposed. 

 Thus it is manifest that the present chemical heterogene- 

 ity of the Earth's surface has arisen by degrees, as the de- 

 crease of heat has permitted ; and that it has shown itself 

 in three forms — first, in the multiplication of chemical com- 

 poujids ; second, in the greater number of difiTerent ele- 

 ments contained in the more modern of these compounds : 

 and third, in the higher and more varied multiples in which 

 these more numerous elements combine. 



To say that this advance in chemical heterogeneity is 

 due to the one cause, diminution of the Earth's tempera- 

 ture, would be to say too much ; for it is clear that aque- 

 ous and atmospheric agencies have been concerned ; and, 

 further, that the affinities of the elements themselves are 

 implied. The cause has all along been a composite one : 

 the cooling of the Earth having been simply the most gen« 

 eral of the concurrent causes, or assemblage of conditions. 

 And here, indeed, it may be remarked that in the several 

 classes of facts already dealt with (excepting, perhaps, the 

 tirst), and still more in those with which we shall presently 



