646 THE POPULAR SCIENCE MONTHLY. 



ated is enough to assure a lively interest in modern petrography, 

 not merely on the part of geologists, but on the part of all intelli- 

 gent persons who love to study the " wonderful wisdom and power 

 of God as shown in his works/' Together they promise far more 

 for the future than has been fulfilled in the past. 



We can not pause long enough to consider each of these four 

 points in succession, but it will be worth our while to glance for 

 a few moments at the last. 



It is a question how far the popularly received distinction 

 between dead and living matter can be made amenable to strict 

 definition as long as we know so little of what the so-called " life- 

 force " is. As far as we can judge of the phenomena presented 

 by the organic and mineral worlds, they differ rather in degree 

 than in kind. This seems like a bold statement, and I am fully 

 aware that it would be totally unwarranted except for the recent 

 disclosures of the microscope in geology. 



The chemistry of life is the chemistry of carbon ; the chemistry 

 of the rocks is the chemistry of silicon. Both are closely allied 

 elements, with the property of forming extremely complex com- 

 pounds, which become more or less unstable with a variation of 

 external conditions. "We are accustomed to regard unceasing 

 change as a sign of life, and to look upon the rocks as unchang- 

 ing, and therefore dead. But the microscope shows that this is a 

 false conception. Not only do the component minerals assume a 

 form as directly inherent in their nature as that of a plant ; but, 

 if the surrounding conditions become unfavorable, they change 

 to other forms, and leave written in the rocks the records of their 

 often complicated histories. The only difference seems to be in 

 the relative slowness of the action. I say " seems to be," because 

 I am by no means convinced of the absolute identity of the two 

 processes. 



In his recent annual address, the well-known President of the 

 Geological Society of London, Prof. John W. Judd, has attempted 

 to throw aside entirely the distinction between crystallized and 

 living matter, and to bring the phenomena of change observed 

 by the microscopist in rocks within the limits of such definitions 

 of life as those of Lewes and Spencer. While we may be unwill- 

 ing to follow him to this extent, we can but confess that the 

 analogy to vital terms and processes recently used with so much 

 power by Prof. Drummond in quite a different sphere is also capa- 

 ble of a valuable application in illustrating some of the modern 

 aspects of geology. We may speak of the embryology of a min- 

 eral, of its histology, morphology, physiology, vitality, and suita- 

 bility to its environment, designating by these terms phenomena 

 which are at least analogous to those which they represent in 

 biology. 



