[ 119 ] 



VI. TJie New Spectrum. By S. P. Langley *. 

 [Plate III.] 



JT'HE writer (at the concluding meeting of the National 

 JL Academy of Sciences on April 18) remarked on the 



disadvantages in the matter of interest of the work of the 

 physicist, which he was about to show them, to that of the 

 biologist, which was concerned with the ever absorbing- 

 problem of life. He had, however, something which seemed to 

 him of interest, even in this respect, to speak of, for it included 

 some indications he believed to be new, pointing the way to 

 future knowledge of the connexion of terrestrial life with 

 that physical creator of all life, the sun. 



He had to present to the Academy a book embodying the 

 labour of twenty years, though at this late hour he could 

 scarcely more than show the volume with a mention of the 

 leading captions of its subject. What he had to say then 

 would be understood as only a sort of introductory description 

 of the contents of the work in question, which was entitled 

 "Volume I. of the Annals of the Astrophvsical Observatory 

 of the Smithsonian Institution." 



In illustration of a principal feature of this book, the 

 Academy saw before them on the wall an extended solar 

 spectrum, only a small portion of the beginning of which, on 

 the left, was the visible spectrum known to Sir Isaac Newton. 

 This was the familiar visible coloured spectrum which we all 

 have seen and know something of, even if our special studies 

 are in other fields. 



It is chiefly this visible part which has been hitherto the 

 seat of prolonged spectroscopic investigation, from a little 

 beyond the violet, at a wave-length of somewhat less than 

 0*4'*, down to the extreme red, which is generally considered 

 to terminate at the almost invisible line A, whose wave-length 

 is 0'7()' i '. On the scale of the actual wave-length of Light, 

 tnen, where the unit of measurement (1^) is one one-thou- 

 sandth of a millimetre, the length of the visible spectrum is 

 0-36*. 



The undue importance which this visible region has assumed, 

 not only in the eyes of the public, but in the work of the 

 spectroscopist, is easily intelligible, being due primarily to 

 the evident fact that we all possess, as a gift from nature, a 



* Abstract of a paper read before the National Academy of Sciences 

 at its Washington meeting, April 18, 1001. ,From an advance proof" 

 communicated by the Author. We are indebted to the author for the 

 plate accompanying this paper. 



