OF ARTS AND SCIENCES : MAY 28, 1867. 315 



after the lapse of more than thirty years, have not been superseded by 

 any others of more practical value. The most frequent cause of ex- 

 plosion was found to be the sudden generation of steam from allowing 

 the water to become too low, and its subsequent contact with the over- 

 heated sides of the boiler. Other assigned causes, such as the genera- 

 tion of gas from the decomposition of water, or the dispersion of water 

 in the form of spray through superheated steam, were successively 

 disproved. 



Early elected into the American Pliilosophical Society, Professor 

 Bache was then associated with Hare, Espy, and other investigators. 

 Erecting for the purpose an observatory in the yard of his dwelling, 

 and with the aid of his wife and his pupil, afterwards his successor, 

 Professor Frazer, he accurately determined, for the first time in this 

 country, the periods of the daily variation of the magnetic needle, 

 and afterwards, the connection of the fitful variations of the direction 

 of the magnetic force with the appearances of the aurora borealis. 

 He also, in connection with Mr. Espy, made a minute survey of 

 the relative change of position of the trees and other objects upturned 

 by a tornado which passed over New Brunswick, New Jersey; and 

 deduced the fact that the tornado was a progressive and ascending 

 column of rarefied air, to which objects at a distance on eitlier side of 

 the track were drawn ; and not a horizontal rotation at the surface, 

 which would tend to throw them outward. In connection with Pro- 

 fessor Courtenay he made a series of determinations of the magnetic 

 dip at various places in the United States. Terrestrial magnetism 

 was with him a favorite subject, to which he continued to make valu- 

 able contributions at intervals during his life. He was also interested 

 in the phenomena of heat ; and he was the first to show, contrary to 

 the generally received opinion, that the radiation, and consequently 

 the absorption, of dark heat is not affected by color. 



It should be noticed that these investigations were prosecuted in tlie 

 intervals of time not occupied by his duties as Professor in the Universi- 

 ty, into which his main strength was heartily thrown, and which absorbed 

 several hours a day, nor claimed by committees of the Franklin Institute 

 and the Philosophical Society. He was enabled to execute these mul- 

 tifarious labors, and to establish his character for promptitude in all 

 his engagements, by rigid system and an exact allotment of his time. 

 He thus found opportunity for all his duties, and, among them, to 

 attend to the claims of friendship and society. 



