REPOKT OF THE SECRETAIJY. 9 



causes with such i)nK'ti('aI (•(»iise<iiieiit'es tliat this chiss oT iiivestiii'a- 

 tioii aims and tends. 



Astro-physics by no means coiitines its investijiation to tiie sun, 

 though tliat is the most im}>oitant subject of its study and one whicli 

 has been undertaken by nearly every leading government of the civil- 

 ized world but the Indted States. France has a great astro-physical 

 observatory at Meudon, and Germany one on an equal scale at l*ots- 

 (him, while England, Italy, and other countries have also, at the na- 

 tional expense, maintained for many years institutions for the prosecu- 

 tion of astro-physical science. 



It has been observed that this recent science itself was almost coeval 

 witli the discovery of the spectroscope, and that instrument has every- 

 where been hirgely emi)loyed in most of its work. Of the heat which 

 the sun sends, however, and which, in its terrestrial manifestations, is 

 the principal ol)]ect of our study, it has long been well known that the 

 s[)ectroscope could recognize only about one-quarter — three-quarters 

 of all this solar heat being in a form which the ordinary spectroscope 

 (;an not see nor analyze, lying as it does in the almost unknown "infra- 

 red" end of the spectrum, where neither the eye nor the photograph 

 can examine it. It has been known for many years that it Avas there, and 

 we have had a rough idea of its amount, with an almost total incapacity 

 to exhibit it in .detail. Our imi^erfect knowledge of this region is at 

 l)resent represented by a few inadequate types of parts of it given in 

 drawings made by hand, where the attempts to depict it at all are even 

 to-day more crude than the very earliest charts of the visible spectrum, 

 made in the infancy of spectroscopic science. 



One of the first i^ieces of work which this observatcn-y has under- 

 taken is to explore and describe what may be properly called " this great 

 unknown region," l»y a method which the writer has recently been able 

 to bring to such a degree of success as to give good grounds for 

 its (continued prosecution and for the hope that a complete map of this 

 whole region will shortly be i)roduced by an automatic and therefore 

 trustworthy i)rocess, showing the lines corresponding to the so-called 

 Fraunhofcr lines in the uiiper spectrum. 



The firstsyear's work of any such observatory must ordinarily con- 

 sist largely in ]»ei'fecting its apparatus and determining its constants, 

 but a ]»ortion of this necessary labor has been deferred in favor of this 

 principal task, of which it is hoped that another year will see the es- 

 sential completion. In this, the present principal scientific work here, 

 all resources of the observatory are, then, for the time being engaged. 



I have acknowledged in a previous report the valuable assistance of 

 Prof. 0. C. ITutcliins, of I)Owdoin College, avIio efficiently aided in in- 

 stalling the api)aratus. Prof, IIut(;hins was obliged to leave in Aug- 

 ust. On the 16th of November Dr. William Hallock was appointed 

 senior assistant. 



At different times during the year, there have been employed as 



