210 On the Decomposition of Light . 



but after it, when his eye had only arrived at the same staffs 

 that the second bov's was in before the operation, he had 

 learnt that the objects were at a distance, and of different 

 colours : that when a child has acquired a new sense, nothing 

 but great pain or absolute coercion will prevent hlrn from 

 making use of it. 



In a practical view, these cases confirm every thing, that 

 has been stated by Mr. Pott and Mr. Ware, in proof of 

 cataracts in children being generally soft, and in favour of 

 couching, as being the operation best adapted for removing 

 them, Tliey also lea4 us to a conclusion of no small im- 

 portance, which has not before been adverted to ; that when 

 the cataract has assumed a fluid form, the capsule, which is 

 naturally a thia transparent membrane, has to resist the 

 pressure of this fluid, which like every other diseased accu- 

 mulation is liable to increase, and distend it, and therefore 

 the capsule is rendered thicker and more opaque in its sub- 

 stance, like the coats of encysted tumours in general. 



As such a change is liable to take place, the earlier the 

 operation is performed in all children, who have cataracts 

 completely formed, the greater is their chance of having 

 distinct vision after the operation. It is unnecessary to point 

 out the advantages to be derived from its being done at a 

 more early age, independent of those respecting the opera- 

 tion itself. 



XXX. On the Decomposition of Light into its most simple 

 Elements, being Part of a JVurk upon Colours. By 

 C. A. Prikur, late a Colonel in the Corps of Engineers. 



[Conll r.r.cd from p. 170.] 



JL iKST I considered, tlial both the nature and quantity of 

 the red, green, and vie/let rays, which I suppose to be the 

 sole elements of ■vhitc light, are absolutely unknown. But 

 I could likewise conceive them transformed into coloured 

 matters of such intensity, or condensation, that the mix- 

 ture of an equal quantity of each should produce exactly 



white. 



In 



