THE PROBLEMS OF GEOLOGY 615 



that the geological results of the past are to be explained by present 

 processes, or the present is the key to the past. While the above 

 conclusions now seem almost axiomatic, we need not go far back to 

 find them astonishing novelties. So far as we are aware, the natural 

 explanation of fossils was first reached by that amazingly versatile 

 genius, Leonardo da Vinci, in the fifteenth century. The conclu- 

 sion that the present is the key to the past required for its formulation 

 the intellect of the great Hutton.^ It was not announced until 1785, 

 and the doctrine was not generally accepted until after Lyell's Prin- 

 ciples appeared in 1830. 



As the science of geology developed, the practice of explaining 

 the phenomena in terms of processes gradually became more common, 

 until, as we have seen, it is dominant in the latest geological text- 

 book. But, as already intimated, the analysis of processes in terms 

 of energy, force, and agent has only begun. It is my belief that at 

 some time in the future a text-book of geology will appear which 

 begins with a discussion of the energies, forces, and agents of geology, 

 the understanding of which is necessary in order adequately to com- 

 prehend processes. It has been stated that the problem of geology 

 is the reduction of the science to order under the principles of physics 

 and chemistry. This is equivalent to saying that the problem of 

 geology is the discussion of the subject in terms of energies, forces, 

 agents, processes, and results. Such a discussion will constitute the 

 principles of geology. 



It is my deep-seated conviction that by the solution of this prob- 

 lem only can geology be so simplified as to be- comprehended with 

 reasonable fulness by the human mind. When this work is done, 

 the broad principles of the science will be capable of statement with 



_i How clearly the great Hutton appreciated the doctrine commonly called that 

 of uniformity is shown by the following quotations from his "Theory of the Earth": 

 "In what follows, therefore, we are to examine the construction of the present earth, 

 in order to understand the natural operations of time past; to acquire principles, by 

 which we may conclude with regard to the future course of things, or judge of those 

 operations, by which a world, so wisely ordered goes into decay; and to learn by what 

 means such a decayed world may be renovated, or the waste of habitable land upon 

 the globe repaired." The concluding sentence of his work is: "The result, there- 

 fore, of our present inquiry is, that we find no vestige of a beginning — no prospect 

 of an end." — Charles Hutton, "Theory of the Earth," Philosophical Traiisactions 

 of the Royal Society of Edinburgh, 1785, p. 218; ibid., p. 304. 



