282 BULLETIN OF THE 



Professor Elle Wartraan, of Lausanne, iu the ScientiBc Memoirs,) 

 supplied original observations on this interesting department of 

 the physiology of vision. 



Miscellaneous Contributions. — Henry's miscellaneous contri- 

 butions to physical science are so numerous and varied, that only 

 a brief allusion to some of them can be afforded. In 1829, he 

 p iblished quite an elaborate " Topographical sketch of the State 

 t.f New York, designed chiefly to show the general elevations 

 and depressions of its surface."* And in later years he devoted 

 much attention to physical geography He performed at various 

 times, a good deal of chemical work (chiefly of an analytical 

 character), — first as Dr. T. Romeyn Beck's assistant,! and after- 

 ward independently, as well as mediately iu directing his own 

 ))upils and assistants. In 1833, he devised an improvement of 

 Wollaston's mechanical scale of the chemical equivalents, for the 

 benefit of his pupils in chemistry: — a contrivance which was 

 much used and highly appreciated at the time. 



The suggestion had been thrown out by more than one astro- 

 nomer, that carefully timed observations on characteristic meteors 

 or " shooting-stars" might be made available for determining 

 differences of longitude between the stations of observation. J 

 For many years however the proposition had been generally re- 

 garded as offering rather a speculative than a practical method of 

 solving a problem of so great nicety. Henry in concert with his 

 lirother-in-law, Professor Alexander, and witli his friend Professor 

 IJache, determined to ascertain by actual trial the availability and 

 value of the system. On the 25th of November, 1835, Professor 

 Bache observing at his residence in' Philadelphia (assisted by 

 I'rofessor J. P. Espy,) — simultaneously with Professor Henry 

 and Professor Alexander, at the Philosophical Hall at Princeton, 

 ihey obtained seven co-incidences: — the instant of disappearance 

 of the meteor being in each case selected as the most accurately 

 attainable epoch. Tliese seven observations (whose greatest dis- 

 crepancies amounted to but a trifle over 3 seconds) gave a mean 

 result of 2 minutes 0.61 second (^time longitude) differing only 



* Tt-ans. Albany Institute, vol. i. pp. 87-112. 



t "Henry was tht-n Dr. Beck's chemical a-^sistaiit, aud already an ad- 

 mirable experimentalist." Address before the Albany Institute, by Dr. 

 (». Meads, May 25, 1871. (Trans. Alhani/ Tnstit. vol. vii. p. 21.) 



X ■' TiiH merit of first stigeesting the use of shooting stars and fire-balls 

 as signals for the determination of longitudes is claimed by Dr. Oll'ers and 

 the (rerman astronomers for L'enzenbeig, who published a work on the 

 !-ubject in 1802. Mr. Bailey however has pointed out a paper jiublishtfd 

 by Dr. Maskelyne twenty years previously, in which that illustrious 

 astronomer calls attention to the subject, and distinctly points out this 

 application of the phenomena.'' This was dated Greenwich, November 

 6ih, 1783. (/,. E. U. Phi. Mag. 1841, vol. xix. p. C54.) 



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