NATIONAL ACADEMY OF SCIENCES. 



apparatus, that used to illustrate his lectures jis well as that more 

 valuable portion which he bad used in his researches, was destroyed. 

 The pecuniary loss he estimated at $15,000. This was the second 

 time he had suffered severely by fire. In 1863 almost the entire 

 edition of his scientific memoirs and essays up to 1844, together 

 with the illustrative plates, were destroyed by fire in the publishing 

 house of Harper & Brothers. 



In 187-'5 Dr. Draper severed his connection with the medical de- 

 partment of the University, but continued his instruction in chem- 

 istry to the undergraduate classes until 1881, the year preceding his 

 death. » 



It has been already stated that Dr. Draper developed very early 

 in life a decided loudness for science and scientific investigation. 

 It is said that his decision to devote himself to the experimental 

 study of nature arose from the accidental observation that in a glass 

 vessel containing camphor beautiful crystals had condensed only on 

 the illuminated side. A desire to understand the cause of this phe- 

 nomenon led him to read whatever books he could obtain which 

 treated of the chemical and mechanical action of light, of adhesion 

 and of capillary attraction, and subsequently to experiment for 

 himself in these and similar subjects. 



Capillary attraction was the subject of his first extended research. 

 dairaut had already shown that the phenomenon was due to the 

 adhesion of the solid for the liquid as compared with the cohesion 

 of the latter, and that if the mutual attraction of a solid and a 

 liquid amount to half the cohesion of the liquid there will he capil- 

 lary depression; but that if this attraction be greater than half the 

 cohesive value the liquid will rise in the tube. Dr. Young had 

 maintained that the bounding meniscus of a liquid was an elastic 

 surface and acted by its tension to elevate or depress the column 

 which it terminated. And Laplace, in the more elaborate memoir 

 contained in his Theoiie de Taction Capillaire, published in the 

 supplement to the tenth book of his Mecanique Celeste, had at- 

 tributed the rise or fall of liquids to the attraction of a thin layer of 

 the liquid immediately adjacent to the walls of the tube. Dr. 

 Draper's attention was first drawn to the subject, as he tells us, dur- 

 ing those tiresome moments of returning health which follow an 

 autumnal fever. " Perhaps," he says, " if there be any merit in these 

 experiments it may hereafter be of service to someone to know that 

 they were begun in sickness and in a land of strangers; that they 



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