Intelligence and Miscellaneous Articles. 



22b 



I proposed to determine the wave-lengths of the lines revealed 

 by the phenomena of phosphorescence by projecting, on the sub- 

 stances above referred to, the spectra furnished by a reticulation. 

 I am indebted to the kindness of M. Mascart for the use of a fine 

 reticulation on metal by Mr. B,utherfurd, as well as for another 

 traced on glass. The first inconvenience met with is that the 

 infra-red region of the first spectrum is entirely superposed to the 

 ultra-violet and luminous region of the second spectrum. These 

 rays are eliminated by the interposition of red glass, which does 

 not arrest the infra-red radiations studied. 



When it was possible to bring to the point the lines of both 

 spectra at the same time, I took advantage of their coincidence to 

 deduce the iDfra-red wave-lengths by doubling the known wave- 

 lengths of the Fraunhofer lines. Thus were determined, with the 

 small reticulation, by transmission, the wave-lengths of two lines : — 

 one 0-000976 millim., near 2F ; the other 0-001098, between 2b 

 and 2D. 



With the reflecting reticulation the simultaneous bringing to 

 the point the two spectra was not possible ; and the position of 

 the infra-red lines was simply taken from the phosphorescent 

 screen by intercepting the more refrangible part of the second 

 spectrum. The corresponding deviations, and consequently the 

 wave-lengths, w r ere determined by a trigonometrical calculation, 

 the elements of which could be directly measured, and were more- 

 over deduced very exactly from the data coresponding to three 

 lines of known wave-length — for example, A, B, and C. By 

 reason of the weakening of the luminous intensity, the measure- 

 ments with the reflecting reticulation could not be extended be- 

 yond the wave-length 0-000918. In short the following numbers 

 were obtained :— 



Lines. 



Wave-lengths. 



Eemarks. 





millim. 









-A 



0-0007604 



(Fraunhofer.) 





Group 

 A. " 



A x * 



A 2 



0-0007819 

 0-0007957 







A 3 * 



0-0008110 1 



Strong extinction- ^ 







,A 4 * 



0-0008360 j 



band. 







^> 



A \* 



0-00086301 

 0-0008850 r 



Luminous region. 



_ Sulphide of 

 calcium. 



Group 



A'. ' 



A' 2 



A' 3 * 



0-0008980 1 

 0-0009180 J 



Strong extinction- 

 band. ) 





A' 4 



0-0009490 



(Interpolation.) 







A'* 



0-0009760 







U'e 



0-0010060 



( Interpolation. ) 





Group (A 



A". \AV.. 



00010500 



(Interpolation.) 





0-0010980 







A • U'V ... 



A*~ 



0-0011760 

 0-001 2200t 



(Interpolation.) 





00013120 "1 

 0-0014440 J 



(Extrapolation.) 





[t A strong extinction-band for blende ; edge very distinct on the less- 

 refrangible side. — Ed. Becquerel.] 



Phil. Mag. S. 5. Vol. 15. No. 93. March 1883. E 



