Transmission of Infra-red Rays and of Radiant Energy. 67 



Table IV. — Calculated Values of Heat Eadiation Penetrating the Eye in 



the Human Subject. 



Wave-length in 

 A.TJ. 



I. 



Percentage of 



heat energy 

 transmitted by 

 cornea of that 

 incident on 

 cornea. 



II. 



Percentage of 

 heat energy 

 reaching the 



to 



anterior surface 

 of lens of that 

 incident on 

 cornea. 



III. 



Percentage of 

 heat energy 

 reaching the 



to 



posterior surface 

 of lens of that 

 incident on 

 cornea. 



IV. 



Percentage of 



heat energy 

 reaching retina 

 of that incident 

 on cornea. 



7 000 



97 '5 



95 



95 



94 "3 



7 500 



97 '5 



95 



94 '6 



91 '3 



8 000 



97 '5 



94 - 5 



93 '6 



89 "6 



8 500 



97 "5 



94 "2 



93 



89 



9 000 



97 '2 



93 *6 



91 '9 



86 '1 



9 500 



94 - 4 



85 "4 



76 '2 



48 



9 750 



93 '6 



83 "1 



72 '5 



41 *2 



10 000 



94 "5 



85 - 8 



77 -2 



50 '3 



10 500 



96 "6 



92 



89 



77 - 6 



11 000 



95 '9 



90 



85 - 1 



67 "7 



11 500 



89 '4 



71 '5 



53 "2 



15 - 9 



12 000 



86 '4 



63 "7 



42 - 2 



7 '9 



12 500 



87 "0 



65 7 



44 "9 



9 '5 



12 750 



87 '3 



65 "6 



44 '8 



10 "6 



13 000 



85 "4 



61 



37 "7 



6 '55 



13 500 



75 '0 



36 '4 



13 '4 



'24 



14 000 



23 '5 



'72 







14 500 



5 "5 



'00 







15 000 



12 '9 



1 *1 







15 500 



28 - 



1 "37 







16 000 



48 - 2 



8 "7 



'73 





16 500 



53 '3 



12 '2 



1 "44 





17 000 



51 "4 



10 



'95 





17*500 



43 -5 



5 -6 



0-30 



— 



18,000 



20-3 



0-42 







18,500 



4-9 









19,000 



2 









19,500 



2 5 









20,000 



4-4 









20,500 



6 









21,000 



7-6 









21,500 



7-1 









22,000 



5 









22,500 



2-5 









23,000 













This Table is shown plotted in fig. 6. 



with the trough filled with water, and then measuring at the same wave- 

 length the deflection without the water. The percentage absorption of the 

 water only was then obtained by stating the first measurement in percentage 

 -of the second. In measuring the deflection without the water the empty 

 trough was not used, as it would introduce an extra pair of glass-air surfaces 

 instead of two glass-water ones. We used instead two glass plates of the 

 ■same thickness as the sides of the trough clamped together with a thin film 



