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116 the magnetic and meteorological elements of the globe. He also made in his summer vacations a magnetic survey of Pennsylvania. Mr. Cramp, afterward the famous shipbuilder, was then a boy in the high school, and assisted Prof. Bache in his observations.

Valuable instruments and methods for performing scientific observations were devised by Bache during this period. He invented an ingenious instrument for determining the dew point, which is especially valuable where readings must be made by persons 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 anemometer 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 American 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 universities, and he found but one exception to the statement that no unusual 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 university he was called to the superintendency of the United States Coast Survey, left vacant by the death of Mr. Hassler. His appointment 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 institutions 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