THE NEW SPECTRUM. 



By S. P. Langley.' 



The writer (at the conchidino- meeting of the National 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 indi- 

 cations he believed to be new, pointing the way to future knowledge 

 of the connection of terrestrial life with that physical creator of all 

 life, the sun. 



He had to present to the academ}^ a book em})odying the lal)or of 

 twenty 3'ears, though at this late hour he could scarcely more than 

 show the volume with a mention of the leading captions of its subject. 

 AVhat he had to say then would be understood as only a sort of intro- 

 ductory description of the contents of the work, in question, which 

 was entitled ''Volume I of the Annals of the Astrophysical Observa- 

 tory 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 por- 

 tion of the beginning of which, on the left, was the visible spectrum 

 known to Sir Isaac Newton. This was the familiar visible colored 

 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, fi-om a little beyond the \iolet, 

 at a wave-length of somewhat less than O.-i'^ down to the extreme red, 

 which is generally considered to terminate at the almost invisil)le line 

 A, whose wave-length is 0. 7()^ On the scale of the actual wave-length 

 of light, then, where the unit of measurement (l*^) is one one-thou- 

 sandtli of a millimeter, the length of the visible spectrmn is o.8♦5^ 



The undue importance which this visible region has assumed, not 

 onlv in the eves of the public, but in the work of the spectroscopist, i.s 

 easily intelligible, ])eingduej3ni ^^ to the evident fact that we all 



'Abstract of a paper read before the National Academy of Sciences at it« Wash- 

 ingtou meeting April 18, 1901. ^^y^ 



