THE PROGRESS OF SCIENCE FROM 1836 TO 1886. 505 



tory during the course of the last half-century. The science of the 

 earth's crust no longer stands isolated as a study by itself : it falls into 

 its proper place in the hierarchy of knowledge as tbe science of the 

 secondary changes, induced under the influence of internal forces and 

 incident energies, on the cooling and corrugated surface of a once in- 

 candescent and more extended planet. I know no better gauge of the 

 widening which comes over the thoughts of men with the processes of 

 the suns than to turn from the rudis indigestaque moles of the " Prin- 

 ciples" and the "Elements" (great as they both were in their own day) 

 to the luminous, lucid, and comprehensive arrangement of Geikie's 

 splendid and systematic "Text-Book." The one is an agreeable and 

 able dissertation on a number of isolated and floating geological facts ; 

 the other is a masterly and cosmically-minded account of the phe- 

 nomena observable on the outer shell of a cooling world, duly consid- 

 ered in all their relations, and fully co-ordinated with all the chief re- 

 sults of all elder and younger sister sciences. 



The battle of uniformitarianism itself, however, was but a passing 

 episode in the great evolutionary movement. That movement began 

 along several distinct lines toward the close of the previous century, 

 and only at last consciously recognized its own informing unity of 

 purpose some thirty-five years ago. From another point of view in 

 connection with its influence upon thought at large the evolutionary 

 crisis has been treated elsewhere in this review by a philosophic 

 thinker ; but in its purely scientific aspect it must also be briefly con- 

 sidered here, forming, as it does, the acknowledged mainspring of all 

 living and active contemporary science. 



Evolution is not synonymous with Darwinism. The whole im- 

 mensely exceeds the part. Darwinism forms but a small chapter in 

 the history of a far vaster and more comprehensive movement of the 

 human mind. In its astronomical development evolution had already 

 formulated itself with perfect distinctness before the period with 

 which we have here especially to deal. The nebular theory of Kant 

 and Laplace was the first attempt to withdraw the genesis of the cos- 

 mos from the vicious circle of metaphysical reasoning, and to account 

 for it by the continuous action of physical and natural principles 

 alone. Our own age has done much to cast doubt upon the unessen- 

 tial details of Kant's rough conception, but, in return, it has made 

 clearer than ever the fundamental truth of its central idea the idea 

 that stars, and suns, and solar systems, consist of materials once more 

 diffusely spread out through space and now aggregated around certain 

 fixed and definite nuclei by the gravitative force inherent in their 

 atoms and masses. As these masses or atoms drew closer together in 

 union around the common center, their primitive potential energy of 

 separation (frankly to employ the terminology of our own time) was 

 changed, first into the kinetic energy of molar motion in the act of 

 union, and then into the kinetic energy of molecular motion or heat, 



