S. P. Langley — Energy and Vision. 



369 



We first give, in table IY, the values of the photometric mea- 

 sures in the prismatic spectrum, reduced to the standard con- 

 ditions above cited. 



Table IV. 

 Showing sensitiveness of the eye to light, as deduced from the "power to decipher fine print. 

 Prismatic (uncorrected) values. 



^=0^-35 



0^-38 



0' '40 



0W5 



I 1 

 0-50 



0^-55 



r -60 



0-65 



0'"-70 



0<"75 



r -768 



S. P. L. 























Mar. 30 







029 



301 



19-31 



19-15 



3-88 



0-28 







F. W. V. 























April 2 





0-13 



9-89 



57-94 



113-3 



15-14 



1-06 



0-27 







April 3 





0-30 



9-88 



154-2 



167-9 



2691 



1-99 



0-43 







April 4 





0-20 



10-88 



154-6 



193-8 



24-62 



223 



033 







April <3 0-0015* 



o-oi7* 



o-n* 











232 





0-005* 



0-0012* 



Mean 0*0015 



o-on 



0-20 



10-25 



122-25 



15833 



22-22 



1-90 



0-34 



0-005 



0-0012 



B. E. L. 





















June 16 





0-24 



30-60 



157-2 



217-0 



36-98 



3-39 



0-17 



o-ooi* 





July 2 0-000* 



0.003* 



0-23 



10-89 



1257 



1423 



33-96 



4-54 



0-73 



0-004* 





July 2 





0-34 



35-38 



186-1 



158-7 



70-16 



5-98 



0-75 







Mean 0-000 



o-ooo 



0-27 



25-62 



1563 



172-7 



47-03 



4-64 



0-55 



0-002 





E. M. 























April 3 





0-35 



3060 



100-1 



146-1 



49-82 



5-85 



1-46 







April 4 





019 



8-34 



4639 



75-27 



42-05 



3-04 









Mean 





0-27 



19-47 



73-25 



110-69 



45-94 



5 45 



1-46 







* Blue (cobalt) glass over slit 



In table Y are the final values, corrected for loss of light by 

 reflection from silver surfaces and reduced to the normal spec- 

 trum. 



Table Y. 

 Photometric values. Normal Spectrum. 



a=0^-B5 



0^-38 



0^-40 



0-45 



0^-50 



0^-55 



r -60 



0^65 



0' a -70 



/ "-75 



0^768 



S. P L. 























Mar. 30 







050 



336 



1461 



1040 



1-62 



0096 







P. W. V. 





















April 2 





0-36 



17-21 



64.76 



85-69 



8-22 



0-44 



0-092 







April 3 





081 



17-18 



172-4 



127-0 



14 61 



083 



015 







April 4 





0-56 



19-11 



172-8 



1467 



1337 



0-93 



o-ii 







April 6 0-0092* 



0-062* 



047* 











97 





0-0015* 



0-0003* 



Mean 0-0092 



0-062 



0-55 



17-83 



13665 



119-8 



12 07 



079 



0-117 



00011 



0-0003 



B. E. L. 





















June 16 





0-65 



5323 175-7 



164-2 



20-07 



1-42 



0058 



•0003* 





July 2 0-000* 



0-011* 



0-63 



18-95 140-5 



107-6 



18-44 



1-90 



025 



•0012* 





July 2 





94 



61-56 208-0 



120-0 



3809 



250 



026 







Mean 0-000 



0-011 



0-74 



44-58 174 7 



130-6 



25 53 



1-97 



0-189 



•0008 





E. M. 























April 3 





0-95 



53-23 



111-9 



119 5 



27 05 



2 44 



0-50 







April 4 





0-52 



14-51 



51-84 



56 94 



22-82 



1-27 









Mean 





074 



33-87 81-87 



83-72 



24-94 



1-86 



0-50 







Am. Jour. Sci. 

 24 



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

 -Third Series, Vol. XXXVI, No. 215— Nov., 1888. 



