Transmission of Infra-red Rays and of Radiant Energy, 61 



index was nearly the same as that of the lens, the values being T46072 and 

 1'42 respectively. 



It does not precipitate the proteids of the lens and yet has marked 

 antiseptic properties. We found that if a cover was put over the trough 

 containing the lens to prevent the evaporation of the carbon tetra- 

 chloride, the preparation remained clear and bright and could have been 

 used on several successive days had this been necessary. We used in 

 our experiments the eyes of the ox, for their large size was a distinct 

 advantage for our purpose. The lens and vitreous were generally removed 

 together by making a wide lateral incision circumferential to the globe and 

 then carefully expressing the contents. We found this method superior to our 

 original technique, in which we removed the lens by the ordinary operation 

 for extraction of cataract. The lens was then carefully separated from the 

 vitreous and was introduced into the trough by gently squeezing it between 

 two plates of glass which were held parallel with the sides of the trough. 

 The carbon tetrachloride was then poured in and the lens prevented from 

 floating up to the surface by a small piece of thick copper wire which was 

 bent so as to fit the upper edge of the lens, the ends of the wire being fastened 

 with plasticine to the top of the trough. The remaining refractivity of the 

 preparation was now neutralised by a concave lens of suitable power fixed 

 outside the trough. On the other side was fastened a tinfoil diaphragm, the 

 aperture in this being freshly cut for each preparation, only so much of the 

 lens being used as could be simultaneously neutralised ; as a rule the aperture 

 measured between 5 and 7 mm. 



Table I. — Table showing Comparative Values of Infra-red Eays of Different 

 Length transmitted by the Lens and by an Equal Thickness of Water. 



A. 



Water. 



Lens. 



Ratio. 



7,000 



11 



8 



0-73 



7,500 



18 



14 



0-78 



8,000 



26 -5 



21 -5 



0-81 



8,500 



35 



31 -5 



0-90 



9,000 



44 



41 



0-93 



9,500 



42 -5 



39 



0-92 



10,000 



51 



52 



1 "02 



10,500 



71-5 



72 



1 -oo 



11,000 



78 -5 



77 



0-98 



11,500 



48 -5 



46 



0'95 



12,000 



41 



45 



1 -io 



12,500 



50 -5 



56 -5 



1 -12 



12,750 



51 "5 



58 



1-13 



13,000 



44 



55 



1 "25 



13,500 



14 



30 



2-1 



14,000 



2 



4 



2 



This Table is shown plotted in fig. 2. 



