SKETCH OF JAMES CROLL. 549 



this office consisted simply in overseeing the various details of the 

 work, and were not phj^sically or mentally laborious ; the hours 

 were short and the labor did not produce mental exhaustion. Yet 

 it did not leave him in quite as fresh condition as his work at 

 Glasgow, and he was obliged to be very precise in the regulation 

 of his life. He had early conceived a distaste for geology as in- 

 volving too much the consideration of details and not giving due 

 prominence to principles, but he had a special interest in the 

 branch which bore upon the object of the particular study in 

 which he was engaged of surface geology or drift in its bearings 

 on glacial and interglacial periods. He had begun his studies in 

 this department before leaving the Andersonian College, and had 

 made frequent excursions into the country in search of glacial 

 phenomena. These excursions were continued with equal success 

 after he went to Edinburgh ; and Mr. James Bennie, who accom- 

 panied him on some of them, has left delightful accounts of them 

 and of Mr. Croll, which are published in connection with Mr. 

 Croll's correspondence. 



In 1865 Mr. Croll suffered an affection which interfered seri- 

 ously and permanently with his capacity for mental work. While 

 bent down, assisting in putting a few tacks into a carpet, he felt a 

 kind of twitch in his head. It did not affect his general health 

 or impair his mental energy, but it was followed by a dull pain, 

 which increased if he persisted in doing mental work for any 

 length of time till it became unbearable ; and he was never able 

 afterward to keep his thoughts concentrated upon a single point 

 as he had been before. Had it not been for this mishap, he says, 

 all the private work which he was able to do during the twenty 

 years that followed "might have easily been done, and would 

 have been, in the course of two or three years." For a few years 

 prior to the publication of Climate and Time it was with the 

 greatest difficulty that he could manage to put together in one 

 day as many sentences as would fill a half page of foolscap, and 

 the appearance of the booi? was delayed on that account. 



In the published correspondence of Mr. Croll appears a letter 

 to him from Charles Darwin under date of July 19, 1871, stating 

 that "Mr. Youmans [Prof. E. L. Youmans], of the United States, 

 is very anxious to get a series of small monographs written by 

 the most competent English authors on various subjects, to be 

 published in the United States, and I suppose in England. Mr. 

 Youmans is in some way connected with the great firm of Apple- 

 tons in New York. He has asked me to name some of the most 

 competent men, and I have thought that you would excuse my 

 giving your name and this note as a kind of introduction. I 

 should add that I do not know on what subject he wishes you to 

 write. I do, however, know that some very good judges think 



