Nipher — Physics During the Last Century. 123 



who will see the beginning of the end. The substitution of 

 some other source of heat and power for coal as it is now 

 used, will tax the resources of the human race, if the civili- 

 zation of to-day is to be maintained. It is customary to put 

 away such thoughts with the optimistic remark that the men 

 of the future will solve the problems of their time as we 

 have solved the problems of our day. But it is also true that 

 there have been former civilizations which have reached 

 their culminations and vanished from the earth. 



Nevertheless, the progress of science during the closing 

 years of the century has been something marvelous, and we 

 are amply warranted in looking forward for still greater things. 



Issued November 13,1901. 



