1886.] Intensity of Radiation through Turbid Media. 379 



below \ L4,000, and that If inches cnts off nearly everything below 

 \10,000. It was therefore determined to use a thickness of -J inch, as 

 up to \14,000 in that case the deflections of the galvanometer would be 

 sufficiently large in both cases to allow the proportion of rays trans- 

 mitted through the transparent and turbid media to be calculated 

 without fear of any grave error due to inaccuracy of reading. 



The spectroscope we have described was used for this purpose, and 

 the source of light used was the crater of the positive pole of the 

 electric light. The opening of the slit was about -^-q inch, and that 

 of the linear piJe about -g\ inch. In the first experiment we described 

 the colour of the crater of the positive pole as seen after passing 

 through the turbid medium was a lemon-yellow, and in the second a 

 deep orange, nearly approaching red. It will be seen that theory 

 and experiment agree within the limits that might be expected. 







Thermopile readings. 



Observed. 



Calculated. 



\ 



1 











A. 















A 







Clear. 



Clear. 







Turbid. 



Clear. 



Turbid. 



Turbid. 







1 



First Experiment. 







524 



14-03 



3-25 



14 



4-31 



4-20 



558 



10 '60 



65 



20-5 



3 - 15 



3'15 



609 



7-72 



12 



29-5 



2-47 



2-42 



652 



5-29 



20 



38 



1-90 



1-91 



684 



4-58 



27 



48 



1-77 



1-77 



720 



3 72 



38-5 



63 



1-63 



1-63 



762 



2 -97 



45 



, 68 



1-51 



1-50 



813 



2-29 



54-5 



77 



1-41 



1-41 



877 



1-68 



6i 



85 



1-33 



1 -33 



960 



118 



58 



73 



1-26 



1-26 



1070 



0-76 



72 



85 



1-19 



1-21 



1170 



053 



39-5 



45 



114 



112 







Second Experiment. 







591 



8-24 



2 



35 



175 



17-75 



636 



6-10 



5 



46-5 



9-30 



9-18 



663 



4-28 



125 



66 



5-2S 



5 25 



774 



2-82 



27-5 



89 



3 24 



3-35 



877 



167 



46 



108 



235 



2 35 



960 



1-18 



47 " 5 



99 



203 



2-02 



1040 



0-855 



55 



101-5 



1-84 



1-83 



1130 



0-613 



53 



89 



1-68 



1-68 



1230 



0-437 



28 



48 



1-60 



1-62 



1320 



329 



13 



20 



1-54 



1 -56 



* These were calculated b y the formula V = It - kc* -4 , using the method of least 

 squares. 



