552 POPULAR SCIENCE MONTHLY. 



had earned a world-wide reputation, ... to turn to his favorite 

 theme of metaphysics ; and now he resumed the subject of which 

 he had never lost sight since his earliest manhood." 



While engaged in his book on Stellar Evolution, and par- 

 ticularly while preparing an article on the Nebular Hypothesis, 

 Dr. CroU wrote to Prof. Alexander Winchell, of Ann Arbor, for a 

 copy of his book on World Life, which he desired to see before 

 publishing. The new book, Stellar Evolution and its Relation to 

 Geological Time, was published in the spring of 1889. It deals 

 mainly with the prenebular condition of matter. 



Dr. Croll was now able to dictate not to write and hardly to 

 read only half an hour a day. But he had one thing to do be- 

 fore his life work could be completed and he accomplished it. 

 This was the publication of his Philosophical Basis of Evolution, 

 a book in which he undertook to state the principle of deter- 

 minism, which he declared to be the foundation stone of evolution ; 

 to examine its relation to Spencer ianism and Darwinism, and to 

 prove that " force, matter, and motion can never be determined 

 by force, matter, and motion," reaching the conclusion that " the 

 universe, in all its beauty, joy, and fullness of life, can never be 

 explained in terms of matter, motion, and force ; so that the 

 whole process of evolution, natural selection included, evidently 

 points to theism." Although it was largely of a metaphysical 

 character, the author claimed that his main conclusions were, 

 without exception, "deduced from facts or from fundamental 

 principles." Dr. Croll substantially exhausted himself in finish- 

 ing the manuscript of this book, and the proof sheets were revised 

 with the help of the Rev. Dr. Caird. The publisher hurried the 

 printing of the work, in order that the author might see a copy 

 of it before he died. A bound copy of it was put into his hand, 

 and he examined it with evident pleasure, observing : " My work 

 is now done. I leave the world without a regret save one " con- 

 cern for the future support of Mrs. Croll. A few days after he 

 had read to him the favorable review of the London Times. Two 

 days before he died, though very weak and exhausted, he was 

 mentally " as clear and alert as in his best days," and eager to 

 discuss with a friend some of Mr. Herbert Spencer's views. 



Dr. Croll was a man of a deeply religious nature, of the strict- 

 est orthodox belief, and of a religion the earnestness and intensity 

 of which impressed his neighbors. His correspondence abounds 

 in expressions marking this as one of the most essential elements 

 of his character. His piety seems to have deepened as he grew 

 older, and was never clearer or more emphatic than in his closing 

 days. 



