﻿98 



S. P. Langley — Unrecognized Wave-lengths. 



offer them under this reserve, now, with the intention of re- 

 turning to them hereafter. 



In the following table we repeat for convenience, the results 

 of certain optical measures made on September 14th, 1885, by 

 Mr. J. E. Keeler with the rock-salt prism, whose refracting 

 angle was on that date 59° 57' 54", and which we have reduced 

 to 60° by the formula given in this Journal for December, 1885. 

 The wave-lengths are those due to Peirce's and Kowland's cor- 

 rections of Angstrom, with which we have been favored by the 

 authors before their formal publication. 



In the succeeding portion of the table, we have the results 

 of measures made with the bolometer in the invisible spectrum. 

 The first column gives the source of heat; the second, the 

 wave-length selected for measurement ; the third, the grating 

 employed ; the fourth, the refracting angle of the prism on the 

 day of observation ; the fifth, the temperature of the appara- 

 tus ; the sixth, the observed deviation ; the seventh, the mean 

 deviation corrected for flexure error and reduced to a refract- 

 ing angle of 60° ; the eighth the resulting index of refraction 

 for rock-salt. 



Source 



of 

 Heat. 



Wave 

 Lengtb. 



Grat- 

 ing. 



Refraeting 

 Angle. 



Temper- 

 ature. 



Observed 

 Deviation. 



Mean Devi- 

 ation Ke- 

 duced to 60°. 



Index of 

 Refraction. 



Sun 

 Arc 



0^-39687 

 •48614 

 •51838 

 •58901 

 •58961 

 •65630 

 •75940 



2x/lD 2 = 

 1-1780 



No. 1 



59° 57' 54" 



a 



u 

 u 



la 



59 57 20 

 59 58 50 



59 57 20 

 59 58 50 



59 58 50 



u 



59 59 34 



24° 

 a 



u 



24 

 26 



24 

 26 



26 



"-I-1 



0-6 

 0*6 



43° 14' 44" 

 41 51 47 

 41 32 52 

 41 02 41 

 41 02 29 

 40 42 56 

 40 22 25 



39 46 

 46 40 

 48 20 



39 31 

 32 

 32 30 



39 24 

 22 40 

 22 24 



24 06 



25 06 



43° 17' 15" 

 41 54 09 

 41 35 13 

 41 05 00 

 41 04 48 

 40 45 13 

 40 24 41 



1-56833 

 1-55323 

 1-54975 

 1-54418 

 1-54414 

 1-54051 

 1-53670 















39 49 18 

 ±12" 



1-5301 ±'0001 



Arc 



3xXD 2 = 

 1-7670 



No. 1 

















39 34 06 

 ±12" 



l-5272±-0001 



Arc 



4xAD 2 = 



2-3560 



No. 1 





u 







u 











Sun 











a 







39 24 18 



±18" 



l-5254±-0001 











