1835.] Composition of White Light. 365 



plete that it can be observed only by their change of position : 

 when the violet fringe is extended to the yellow, by with- 

 drawing the prism, it converts it to white. In this experi- 

 ment there are no fringes from the black to interfere with 

 the red ; and the red being less refrangible than any part of 

 the blue, does not overtake it ; but the violet being more 

 refrangible than the green, with which it is combined to 

 form the blue, leaves it to form a union with the unmixd 

 green adjoining ; and, when still further extended, with 

 the yellow beyond it. By directing the prism across the 

 stripes diagonally, the breadth of the fringes may be regu- 

 lated without altering the distance of the prism. 



In the multitude of experiments from which these have 

 been selected, I have never observed any thing which gave 

 me the least reason to doubt the correctness of the theory 

 by which I have attempted to explain them. The colours 

 which are considered compound have submitted to decompo- 

 sition, with the results which might have been expected, 

 whenever the proper methods for the purpose have been 

 adopted ; while the simple colours, red, green, and violet 

 have withstood every test which has been applied to them : 

 these colours may be weakened, or they may be wholly re- 

 moved in the course of our experiments, but they are never 

 changed. It is necessary to observe that we are here speak- 

 ing of the primary colours in a state of purity ; when they 

 are diluted with white light, the decomposition of this light 

 by coloured media, produces the appearance of modifications, 

 which however, are readily removed by such methods as 

 leave no doubt as to their cause. 



P. C. 

 Weston Super Mare, August 31 st, 1835. 

 To the Editor of the Records of General Science, 



Article IV. 



The action of Saline Solutions on Fibrin. By Harry Rainy, 

 M.D., Lecturer on the Theory of Physic in the University 

 of Glasgow. 



( To the Editor of the Records of General Science. J 

 Sir, 



You will oblige me by giving the following remarks a 

 place in your Records of General Science. They were partly 



