24 SALMON FISHING IN THE TWEED 



as his Bill had failed, it was not necessary to trouble 

 me any farther on the subject. 



This letter contains evidence that Sir David 

 Brewster's experiments were made previously to its 

 being written ; and when I had thought of publish- 

 ing, being desirous to know the exact time when 

 they were made, I wrote to Sir David to call his 

 attention to the subject. His answer, dated 16th 

 of April, 1840, was as follows : 



" I am pretty sure that my experiments on the 

 structure of the crystalline lens of the parr, which 

 is identical with that of the salmon, were made 

 previous to 1828. 1 I remember well your stating 

 to me that when the silver scales of the young 

 salmon (which in Roxburghshire we call smouts) 

 were carefully rubbed off, the colours of a darker 

 hue which characterise the parr were invariably and 

 distinctly seen. I think you showed me the experi- 

 ments, but I am not sure of this. With the view 

 of confirming this your theory, or of over-turning 

 it, I mentioned to you that the fibres of the lens of 

 the salmon," &c. 



Then follows the account of his experiments, as 

 detailed a little farther on. 



Besides the reasons mentioned in the above letter, 

 there were other causes which influenced me in the 

 opinion I had formed ; the two principal of which 

 were 



Firstly, That no one ever saw a clear silver- 



1 The date of Mr. Kennedy's Bill, which I have but just ascertained, 

 proves that they were made in or before the year 1825 ; whereas Mr. 

 Shaw's first account of his interesting experiments appeared in the 

 "New Edinburgh and Philosophical Journal" for 1836, vol. xxi. p. 99. 

 eleven years after. 



