EEPORT OF THE SECRETARY. 29 



determined positions, and we may be said now to know, by the aid of 

 the bolometer and the labors of the observatory, more lines in this 

 invisible spectrum than were known in the visible one up to the great 

 research of Kirchoff and Bun sen, which opened the era of modern 

 spectrum analysis. Moreover, these lines, the exactness of whose 

 determination has now reached a surprising degree of perfection 

 through the recent improvements in the delicacy as well as the pre- 

 cision of both bolometer and galvanometer, and through other improve- 

 ments in the apparatus (improvements due principally to the present 

 Aid acting in charge), depend not only on the instruments, but on the 

 labors of those who have used them, the comparator measurements 

 alone having included, as stated in the body of the report, about 44,000 

 separate observations. 



A great deal of other work has been done at the observatory, but 

 nothing which in importance and present and prospective interest com 

 pares with this main research in the infra-red spectrum, which is now 

 known throughout nearly the whole of the invisible portion of the solar 

 energy, and extends through a range of wave lengths considerably over 

 twelve times that known to Sir Isaac Newton, the present exact knowl- 

 edge of this region being due not exclusively, but it may properly be 

 said principally, to the labors of this observatory. 



I call attention in this connection to the interesting remarks made in 

 the report to the effect that very marked changes of absorption have 

 been observed at various parts of the infra-red spectrum. In one part 

 of the invisible region a decrease in absorption, amounting to nearly 

 half the total, took place in February, and this abnormal state con- 

 tinued until May, when the usual condition gradually returned. As 

 this change is found to occur yearly at about the same period, the 

 idea presents itself that the growth of vegetation, so rapid in these 

 months, may abstract from the air large quantities of vapor active in 

 absorption at this point in the spectrum, but this interesting possibility 

 has not yet, it will be understood, been fully verified. 



In this, however, and other discoveries of a similar nature we have 

 the earnest of the fulfillment of long cherished hopes, already alluded 

 to by me, for the ultimate benefit of these researches, not only to science, 

 but to concerns of practical moment and even of national utility. 



NECROLOGY. 



Gardiner Greene Hubbard was born in Boston August 25, 1822, and 

 died in Washington on December 11, 1897. After preparation in the 

 Boston schools he entered Dartmouth College, being graduated bache- 

 lor of arts in 1841. He studied law in Cambridge, and was admitted 

 to the bar of Boston, where he practiced his profession for twenty 

 years, and later at the national capital. 



His first interest in educational and scientific matters appears to 

 have been connected with the improved education of the deaf, and he 



