u6 THE POPULAR SCIENCE MONTHLY. 



the magnetic and meteorological elements of the globe. He also 

 made in his summer vacations a magnetic survey of Pennsyl- 

 vania. Mr. Cramp, afterward the famous shipbuilder, was then 

 a boy in the high school, and assisted Prof. Bache in his obser- 

 vations. 



Valuable instruments and methods for performing scientific 

 observations were devised by Bache during this period. He in- 

 vented an ingenious instrument for determining the dew point, 

 which is especially valuable where readings must be made by per- 

 sons without special scientific training. Only much later did he 

 learn that the principle of the device had already been used by 

 Belli, of Milan. He also introduced a modification of Osier's ane- 

 mometer and invented a thermoscope of contact, both of which 

 avoided difficulties involved in the use of previous instruments. 



The way in which a man conducts a controversy is always a 

 severe test of his character. Bache had one with Denison Olmsted 

 on the periodical recurrence of meteors. Prof. Gould, in his Amer- 

 ican Association memoir, thus describes the occurrence: "Mr. 

 Bache maintained that there was no recurrence in 1834; Prof. 

 Olmsted, on the other hand, maintained the reverse. Prof. Bache 

 instituted special inquiries at the military posts (where, of course, 

 sentinels were on duty) along all the frontiers of the United States, 

 also among the night police of various cities, and at the universi- 

 ties, and he found but one exception to the statement that no un- 

 usual number of meteors was seen. Of this controversy Bache 

 wrote, in 1846 : 



" ' There is something yet to be found out on this subject which 

 may reconcile our opinions. Neither I nor any of those watching 

 with me, or for me, have seen an unusual number of meteors on 

 the night of the 12th of November in any year since the great 

 night at Philadelphia, and we have taken great pains to be sure. 

 Yet I can not doubt the testimony as given for some other places. 

 ... I had a complimentary letter from the professor in regard to 

 my manner of conducting the controversy, which I valued more 

 highly than if I had gained the victory/ " 



The year after Prof. Bache resumed his old position at the uni- 

 versity he was called to the superintendency of the United States 

 Coast Survey, left vacant by the death of Mr. Hassler. His ap- 

 pointment to this position was first suggested by members of the 

 American Philosophical Society, and the nomination was fully 

 concurred in by the other principal scientific and literary institu- 

 tions of the country. 



Although the Coast Survey had been founded a quarter of a 

 century, the policy of Congress toward it had been changeable 

 and its appropriations limited. It had been suspended fifteen 

 years of that time, so that its work was but just begun. The At- 



