Prof. S. P. Langley on Energy and Vision. 13 



In Table V. are the final values, corrected for loss of light 

 by reflexion from silver surfaces and reduced to the normal 









us. 



Table V. 

 Photometric Values. Normal Spectrum. 







> 



= 



0'*-35 



Of^-SS 



0'^-40 



0'^-45 



0''-50 



Of^-55 



0'*-60 



0^-65 



0*^-70 



0'^-75 



0'^-768 



iaa 



.L. 



•.30. 









0-50 



3-36 



14-61 



10-40 



1-62 



0-096 







\ V \. V. 

 Lpr dl 2. 

 -V fil 3. 

 Lp. -11 4. 

 .pi il 6. 

 4"' m ... 



0-0092* 

 0-0092 



0-062* 

 0062 



0-36 



0-81 



0-56 



0-47* 



0-55 



17-21 



17-18 

 1911 



17-83 



64-76 

 172-4 



172-8 



136-65 



85-69 

 127-0 

 146-7 



119-8 



8-22 

 14-61 

 13-37 



12-07 



0-44 

 0-83 

 0-93 

 0-97 

 0-79 



0-092 



0-15 



0-11 



0117 



0-0015* 

 0-0015 



00003* 

 0-0003 



B:]^.L. 



June 16. 

 July 2. 

 July 2. 

 Mean ... 



0000* 

 0000 



0011* 

 0011 



0-65 

 0-63 

 0-94 

 0-74 



53-23 



18-95 

 61-56 



44-58 



175-7 

 140-5 

 208-0 

 174-7 



164-2 



107-6 

 120-0 

 130-6 



20-07 

 18-44 

 38-09 

 25-53 



1-42 

 1-90 

 2-50 

 1-94 



0-058 



0-25 



0-26 



0-189 



-0003* 

 •0012* 



-0008 





M. 



aipril 3. 

 April 4. 

 Mean ... 







0-95 

 0-52 

 0-74 



53-23 

 14-51 

 33-87 



111-9 



51-84 

 81-87 



110-5 

 56-94 

 83-72 



27-05 

 22-82 

 24-94 



2-44 

 1-27 

 1-86 



0-50 

 0-60 







* Blue (cobalt) glass over slit (Sj). 



In this table we have, first, the wave-lengths corresponding 

 to the observed angles of deviation, these values reachino- 

 from0''-35 in the ultra-violet to C*-?? near Fraunhofer's A on 

 the extreme border of the visible red. It is to be observed, 

 however, that the great mass of the observations which were 

 taken without disturbing the slit reach from 0''-40 in the 

 deep violet to O'^'TO in the deep red. The figures correspond- 

 ing to 0'^-35, 0'^-38, 0'^-75, O*^-?? are extremely difficult to obtain 

 with precision and are given here as supplementary to the 

 others. There are four observers : — 



S. P. L., whose eye is somewhat long-sighted (making 

 convenient the use of convex glasses of half-metre focus) and 

 not sensitive to very feeble light ; eyes otherwise believed to 

 be in normal condition. 



F. W. v., near-sighted, using glasses whose negative focus 

 is 14 centim. The eye appears to be much less sensitive to 



