GEORGE FREDERICK BARKER. xxi 



the great range of subjects about which he had informed himself, 

 and upon which he was equipped to accompHsh vakiable scientific 

 work. His alertness of mind, even a few years before his death, 

 is plainly evident in his later papers on such subjects as radio- 

 activity and intra-atomic energy in 1903, and before that time in 

 his discussion of liquefied air, Roentgen rays, wireless telegraphy, 

 monatomic gases, etc. 



From the fact that he survived many of his contemporaries and 

 associates in scientific work, it was natural that it should have 

 fallen to his lot to prepare memoirs to some of these to whom he was 

 most closely drawn. How well the work was done, with what con- 

 scientious care as to facts, and in what personal estimation he held 

 these friends, can only be understood by a careful reading of these 

 memoirs. Coupled with tender remembrances, they show a sincere 

 admiration for the accomplishments, the discoveries and researches 

 which he so ably describes. He spared no pains to bring out clearly, 

 and often in detail, the things for which his friend was best known, 

 his scientific methods and results, and throughout all this his keen 

 personal interest and afifectionate regard is manifested. This large- 

 ness of view and willingness to devote much time and effort to assist 

 in securing that place in science which his friends' work seemed to 

 him to deserve, appears to the writer as quite characteristic, and 

 implies a most generous spirit. Examples of the truth of this 

 will be found in his memoirs of John William Draper, and of his 

 son. Dr. Henry Draper, read before the National Academy of Sci- 

 ences, one in April, 1886, and the other in April, 1888. The elder 

 Draper died early in 1882, and his son Henry late in the same year. 



The splendid achievements of the elder Draper in science and 

 philosophy are well known, and are most ably dealt with in the 

 memoir referred to, while Dr. Barker's close personal relations with 

 Henry Draper gave him excellent opportunities for obtaining the 

 biographical material which he has incorporated in the memoirs. 

 Henry Draper devoted himself to optical and astronomical science, 

 constructing improved instruments and devising new methods. Of 

 him Dr. Barker writes from the standpoint of a warm personal 

 friend telling of a most fruitful career too soon closed; a scientist of 



