258 MEMORIAL <>!'' JOSEPH HENRY. 



Meteorology. — From an early date Henry took a deep interest 

 in the study of meteorology: nol only on account of it- practical 

 importance, but from its relation to cosmical physics, and because 

 from the very complexity and irregularity of its conditions, it 

 challenged further investigation and stood in need of larger gener- 

 alizations. Ilis early association with 1 *r. T. Romeyn Beck in 

 the first development of the system of meteorological observations 

 established in the State of New Turk, has already been referred to 

 in the sketch of his " Early Career." ( Page -1 2.) This active and 

 zealous co-operation continued from 1827 to 1832; or as long as he 

 resided in Albany. 



In September of 1830, he commenced a series of observations 

 for Professor Renwick of Columbia College, to determine the 

 magnetic intensity at Albany. With the assistance of his brother- 

 in-law, Professor Stephen Alexander, these observations were con- 

 tinued daily for two months.* In April, 1831, a second series of 

 observations was commenced; in the course of which \\\> attention 

 was attracted by a great disturbance of the needle during the 

 time of a conspicuous "aurora'' on the 19th of April, 1831. At 

 noon of the 19th the oscillations were found to be perfectly accord- 

 ant with previous ones, but at 6 o'clock p. m. a remarkable increase 

 of magnetic intensity was indicated. At 10 o'clock of the same 

 evening, during the most active manifestation of the aurora, the 

 oscillations of the needle were again examined. " Instead of still 

 indicating as at (i o'clock an uncommonly high degree of magnetic 

 intensity, it now showed an intensity considerably lower than usual.'' 

 Thus, designating the normal intensity at the place as unity, at fi 

 o'clock it had increased to 1.024, and at 10 o'clock hail subsided to 

 0.993, which according to Ilansteen's observations is the usual 



*The needles employed in these observations were a couple received by Professor 

 Ki \ u icK ir'ii ii t ';i|it. Sabine,— one or which had belonged to Professor Hanstej n 

 of Xorway. "They were suspended according to the method of Hansteen in a small 

 mahogany box, byasingle fiber of raw silk, 'flu- box was furnished with a ^lass 

 cover, ami had a graduated an- of ivory on the bottom to marl; the amplitude of the 

 vibrations, [n using this apparatus, the time of three hundred vibrations was noted 

 by a quarter-second watch, wall regulated to mean time; a register being made at. 

 the end of every tenth \ Ibration, and a mean deduced from tin- whole, taken as the 

 true time of the three hundred vibrations. Experiments carefully made with this 

 apparatus were found susceptible of considerable accuracy;'* the individual observa- 

 tions not differing from tin' mean number, ordinarily more than one-thousandth. 

 iSiUiman's.lm. Jour. Set. April, 1832, vol. xxii. p. 145.) 



