Prof. Sylvester's Notes on the Optical Theory of Crystals, 341 



ducts of this decomposition, he would, perhaps, have been the 

 first to make the beautiful discovery, which fifteen years after- 

 wards was made by M. Wohler in the artificial production of 

 an animal matter; but the small quantity of matter upon which 

 he operated, did not permit him to analyse completely a sub- 

 ject to which he never afterwards returned. 



It is exceedingly curious to see a substance of such a sim- 

 ple composition as cyanogen, a substance which is placed by 

 its characters in the system of chemistry, not at the side, but 

 in the very middle of the elements, giving birth, in reacting- 

 upon water, to so many different products. 



In admitting for the black matter the formula Ng Cg Hg O4, 

 we can explain the decomposition of cyanogen in water by the 

 following equation : ' 



1 atom urea N4 Cg Hg O^ 



6 atoms prussic acid Ng Cg Hg 



4 atoms carbonic acid C4 Og 



2 atoms ammonia N^ Hg 



1 atom oxalate of ammonia Ng Cg Hg O4 

 1 atom black substance Ng Cg H g O4 



^22 ^22 Hag O18 



LVII. Notes to Analytical Development^ S^c, By J. J. Syl- 

 vester, of St. John's College Cambridge, Professor of Natural 

 Philosophy in University College, London,'^ 



Note 1. 



IN the paper above adverted to, I showed that the meridian 

 plane, i. e. the plane contaming the ray and normal, always 

 passed through ^a line of vibration in the corresponding point. 

 Now the line of force called into action by a displacement in 

 the line of vibration clearly lies in this very plane; for the re- 

 solved part of it lies in the line of vibration itself. 



Harmony and analogy concurred in making me suspect 

 that as two of these four lines are perpendicular to each other, 

 so are also the other two, or in other words, that the ray is 

 always perpendicular to the direction of unresolved force. 



The following investigation verifies this conjecture. 



Let a:,y, z be the coordinates of a point taken at distance 

 unity from the origin and in any line of vibration ; then the 

 cosines of the angles made by the line of force with the axes 

 are as a~ x: b^y: c'^ z respectively. 



Let a be the inclination between the line of vibration and 

 the line of force, then 



* Communicated by the Author: see vol. xi. p. 461 etscq. and present 

 volume, p. 73 et seq. 



