270 MEMORIAL <>F JOSEPH HENRY. 



differing deflections of the galvanometer needle "that the spol 

 emitted less heat than the surrounding parts of the luminous disk.''* 

 A brief account of the result- obtained by these researches given in 

 a letter to his friend Sir David Brewster, was read by the latter 

 at the ( !ambridge Meeting of the British Association in June, 1845.1 

 The determinations arrived at have been fully confirmed by the 

 later observations of Secchi and cithers. £ 



In 1845, lie contributed a paper to the Princeton Review, on 

 " ( tolor Blindness ;" which although in the modest form of a literary 

 review nt' two Memoirs then recently published, (that of Sir David 

 Brewster in the Philosophical Magazine; and that of Professor Elie 

 Wartman, of Lausanne, in the Scientific Memoirs,) supplied 

 original observations mi this interesting department of the physi- 

 ology uf vision. 



Hfisci llaneous Contributions. — Henry's miscellaneous contribu- 

 tions to physical science an 1 so numerous and varied, that only a 

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

 published quite an elaborate "Topographical sketch of the State of 

 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 also made some geological 

 explorations and observations in the Stateof New York, lie per- 

 formed at various times a good deal of chemical work (chiefly of 

 an analytical character), — first as Dr. T. Romeyn Beck's assistant, || 



*Pi'OCced. Am. Phil. Soc. June 20, 1845, vol. iv. pp. 17:5-176. 



f Report lint. Assoc. 1845, part ii. p. 6. 



XV. Angf.lo Secchi— during the years LS4S and 1849, (then a young man of thirty.) 

 was Professor of Mathematics at the College of I leorgetown, D. C. and in the pre- 

 paration "i iii- "Researches on Electrical Rheonietry," published in the third 

 volume of the Smitteonian Contributions, (art. ii. 60 pp.) in- received from Henry the 

 friendlj assistance "t apparatus and suggestions. Ii i- interesting t" refer t" 

 Henry's introduction •■! Professor Secchi's first researches i<> the attention ol the 

 Regents "i the Smithsonian Institution, when the name was as yet wholly un- 

 known t<» iIm' scientific world. "Another memoir is by Professor Secchi, a young 

 ttalian <>f much ingenuity and learning, n member of Georgetown College. It 

 consists of :i new mathematical investigation of the reciprocal action "l two 

 ^iiiviiiiH' currents on each other, and of the action of a current "ii the pole of a 

 magnet." I Smithsonian Report for 1849, p. 172, S. ed. and p. 164, H. R. ed.) Professor 

 Secchi was appointed Director of the Observatory at Rome, in 1850. 



': Trans. Albany Institute, vol. i. pp. S7-112. 



I "Henry was then Or. Beck's chemical assistant, and already an admirable 

 experimentalist." Address before the Albany Institute, by Dr. O. Meads, .May 2.'., 

 1871. i Trans. Albany Institute, vol. vii. p. 21.) 



