424 THE INSTABILITY OF THE HOMOGENEOUS. 



that, as an average fact, the simple combinations can exist 

 at a higher temperature than the complex ones. And this is 

 wholly beyond question. Thus it is manifest that the 



present chemical heterogeneity of the Earth's surface has 

 arisen by degrees as the decrease of heat has permitted ; and 

 that it has shown itself in three forms — first, in the multipli- 

 cation of chemical compounds; second, in the greater num- 

 ber of different elements contained in the more modern of 

 these compounds; and third, in the higher and more varied 

 multiples in which these more numerous elements combine. 

 Without specifying them, it will suffice just to name the 

 meteorologic processes eventually set up in the Earth's at- 

 mosphere, as further illustrating the alleged law. They 

 equally display that destruction of a homogeneous state 

 which results from unequal exposure to incident forces. 



§ 1 52. Take a mass of unorganized but organizable mat- 

 ter — either the body of one of the lowest living forms, or the 

 germ of one of the higher. Consider its circumstances. 

 Either it is" immersed in water or air, or it is contained with- 

 in a parent organism. Wherever placed, however, its outer 

 and inner parts stand differently related to surrounding 

 agencies — nutriment, oxygen, and the various stimuli. But 

 this is not all. Whether it lies quiescent at the bottom of 

 the water or on the leaf of a plant; whether it moves through 

 the water preserving some definite attitude; or whether it is 

 in the inside of an adult ; it equally results that certain parts 

 of its surface are more exposed to surrounding agencies than 

 other parts — in some cases more exposed to light, heat, or 

 oxygen, and in others to the maternal tissues and their con- 

 tents. Hence must follow the destruction of its original 

 equilibrium. This may take place in one of two way-. 

 Either the disturbing forces may be such as to overbalance 

 the affinities of the organic elements, in which case there 

 result those changes which are known as decomposition ; or, 

 as is ordinarily the case, such changes are induced as do not 



