88 PHYSICS OF MATTER 



term! With what amazement does he then see the machine begin to 

 compute the squares or the cubes of the numbers it had previously 

 disclosed! The date when that machine was created and set to work 

 has been rudely called in question by the new and seemingly lawless 

 behavior of which it appears to be capable. And yet the observer still 

 feels that the principles of mechanism have not been shaken by this 

 unlooked-for disclosure. He again begins his work, with broader 

 conceptions of the plan of this machine. And his subsequent work 

 is along precisely the same lines, and by the same methods as his 

 previous work. 



It is in exactly this way that all scientific work has proceeded, 

 and I wish to point out a few interesting cases of this kind. I find it 

 impossible to do this without presenting the present aspect of these 

 problems in connection with the work of the past. This plan gives 

 a perspective which not only adds to the interest but to the clearness 

 of the presentation. 



The nebular hypothesis was an attempt by Kant, Laplace, and 

 Herschel to trace the evolution of the solar system from a glowing 

 mass of incandescent vapor or gas. As the theory was considered 

 and developed, an immense number of correlated phenomena were 

 found to be in harmony with this hypothesis, and a few discordant 

 phenomena were also found. The operation was, moreover, based 

 on a few fundamental and well-established laws, governing the pre- 

 sent condition of the system; such as gravitation, radiation of heat, 

 etc. The case became more and more convincing, as the knowledge 

 of the last century was applied. All of this caused the astronomers 

 and physicists to find it very easy to give to the hypothesis their 

 tacit assent. 



Later, Sir William Thomson, now Lord Kelvin, took up the ques- 

 tion of underground temperature, and determined the limit in time 

 since which the earth must have begun to solidify. He also assumed 

 that the present order of things had come down to us from the past, 

 and that the present order of things consisted in the radiation of 

 heat from a cooling earth. 



The time-interval which Kelvin thus determined was in entire 

 harmony with the nebular hypothesis, but the results were received 

 with something like consternation by geologists, and those who had 

 followed Darwin in the study of the evolution of organic life upon 

 the earth. Afterwards Kelvin sought to show that the process of 

 solidification might have required but a short interval of time, and 

 the evolutionists have found that evolution goes on by steps or sudden 

 changes rather than by a continuous succession of imperceptible 

 increments. 



The geologists have never been reconciled to Kelvin's results, and 

 their protests have of late seemed to be on the increase. Of late the 



