090 THE POPULAR SCIENCE MONTHLY. 



cal .and chemical, geographical and biological and throws it on the 

 pages of that Great Stone Book on which the past history of our globe 

 is recorded. And while Astronomy is of all sciences that which may 

 be considered as most nearly representing Nature as she really is, 

 Geology is that which most completely represents her as seen through 

 the medium of the interpreting mind ; the meaning of the phenomena 

 that constitute its data being in almost every instance open to ques- 

 tion, and the judgments passed upon the same facts being often differ- 

 ent according to the qualifications of the several judges. No one who 

 has even a general acquaintance with the history of this department 

 of science can fail to see that the geology of each epoch has been the 

 reflection of the minds by which its study was then directed ; and 

 that its true progress dates from the time when that " common-sense " 

 method of interpretation came to be generally adopted which consists 

 in seeking the explanation of past changes in the forces at present in 

 operation, instead of invoking the aid of extraordinary and mysterious 

 agencies, as the older geologists were wont to do whenever they 

 wanted like the Ptolemaic astronomers " to save appearances." 

 The whole tendency of the ever-widening range of modern geological 

 inquiry has been to show how little reliance can be placed upon the so- 

 called " laws " of stratigraphical and paleontological succession, and 

 how much allowance has to be made for local conditions. So that, 

 while the astronomer is constantly enabled to point to the fulfilment 

 of his predictions as an evidence of the correctness of his method, the 

 geologist is almost entirely destitute of any such means of verification. 

 For the value of any prediction that he may hazard as in regard to 

 the existence or non-existence of coal in any given area depends not 

 only upon the truth of the general doctrines of geology in regard to 

 the succession of stratified deposits, but still more upon the detailed 

 knowledge which he may have acquired of the distribution of those 

 deposits in the particular locality. Hence no reasonably-judging man 

 would discredit either the general doctrines or the methods of geology, 

 because the prediction proves untrue in such a case as that now about 

 to be brought in this neighborhood to the trial of experience. 



We have thus considered man's function as the scientific interpre- 

 ter of Nature in two departments of natural knowledge, one of which 

 affords an example of the strictest and the other of the freest method 

 which man can employ in constructing his intellectual representation 

 of the universe. And, as it would be found that in the study of all 

 other departments the same methods are used either separately or in 

 combination, we may pass at once to the other side of our inquiry 

 namely, the origin of those primary beliefs which constitute the 

 groundwork of all scientific reasoning. 



The whole fabric of geometry rests upon certain axioms which 

 every one accepts as true, but of which it is necessary that the truth 

 should be assumed, because they are incapable of demonstration. So, 



