548 Royal Societij. 



dition. — 4. Of the nature of certain disturbing and dazzling effects 

 of vision by strong light. — 5. Of the phaenomena of certain spectral 

 illusions. — 6. As to the practical use of the process of examining the 

 ocular spectra, for the determination of quantities of light relatively 

 intercepted by different portions or thicknesses of glass or other trans- 

 parent media. — 7. For assisting in the determination of the relative 

 degrees of illumination of lamps, candles, &c., and of quantities of 

 light reflected from opake objects. — 8. For aiding in the selection 

 and harmonizing of colours in ornamental and decorative depart- 

 ments of art. — 9. For the examination of the condition of the inte- 

 rior of the eyes in certain states of disease. The author having had 

 the opportunity of trying this process in case of amaurosis, found 

 that it afforded a perfect picture of defects in the surface of the 

 retina of the eyes separately, when there was no visible defect, and 

 when the patient had no other perception of a diseased eye, or patch 

 on the retinal surface, except the partial distortion or interruption 

 of vision. Founded on this, the author suggests a plan of scotome- 

 trical examination of retinal defects, by which not only the accurate 

 form and relative proportions of diseased patches on the retina may 

 be deteimined, but their actual dimensions may probably be deduced. 



" Note on Nitro-glycerine." By A. W. Williamson, Ph.D., F.C.S., 

 Professor of Practical Chemistry in University College. 



This compound is formed by acting upon glycerine with a mix- 

 ture, in equal volumes, of concentrated nitric and sulphuric acids, 

 the glycerine being added by a few drops at a time. 



It is heavier than water, in which it is slightly soluble, and is 

 soluble in alcohol and in aether. 



From its proneness to decomposition in drying, even by the air- 

 pump, a complete analysis could not be made, but a qualitative ex- 

 amination of the relative amounts of carbon and nitrogen gave the 

 following results : — 



1. 2. 3. 4. 



Volumes of mixed gases 101 91*5 99 97 



Volumes of nitrogen not absorbed by potash. . 32 30'3 34 33 



Carbonic acid absorbed by potash 69 61 65 64, 



1. 2. 3. 4. 5. 



Mixed gases 178 194 173 194 192 



Nitrogen 61 66 58 65 65 



C0« 117 128 115 129 127 



From these results the following formula was deduced : — 



C6H8 06 + 3NO*=C6 3^Q,06-f3HO. 



It would therefore appear that 3H are replaced by 3NO4. 

 On boiling this compound with concentrated solution of potash, it 

 is decomposed into glycerine and nitrate of potash. 



" On a new Phosphite of ^thyle." By A. W. Williamson, 

 Ph.D. &c. 



The following results were obtained by Mr. Railton in an in- 

 vestigation undertaken in connexion with the idea that the water 



