EXPERIMENTS ON THE SALMON SMOLT. 95 



large tank is formed close on the bank of the Dee, through which 

 part of that water has a free ingress and egress ; and the tank is 

 so constructed by machinery and wire netting at each end, that 

 when the Dee rises the water in the tank rises also, and vice 

 versa. Into this tank we put the fry, at the same time knowing 

 it to be the salmon-fry by observing the old salmon deposit their 

 spawn, which we can do at any time during the spawning season. 

 The young fry, when put into the tank, are about half an inch 

 long, and have at that time the pea attached to their belly. The 

 first year they do not assume much of the parr, but the second 

 year they are decidedly so, by hundreds of comparisons with parr 

 taken out of the Dee, and the third year they become what we 

 call the young salmon-fry, and from four to five inches long, and 

 quite change their colour from the parr to a silvery one ; at this 

 stage they go down to the salt water. Were we to confine them 

 longer than the third year, by many experiments, they fall very 

 much off. Another proof of the parr being the young salmon is, 

 that no man ever saw a parr higher up a river than where a salmon 

 can go. 



" Grillom tells me his first experiments were in 1835-6. In that 

 year he put fry into an inland lake ; they did very well until the 

 third year, and then fell off, and eventually perished. He also 

 tells me that he would not believe the parr to be young salmon 

 until he proved it by his own experiments. 



" Now I doubt much if you can make out this hurried scrawl ; 

 but if you can I hope it will tend to throw some light on the 

 subject ; if so, let me hear from you. 



" Your family are well. I had the pleasure to sup in company 

 with your father last evening. My wife joins me in kind regards 

 to you, and believe me, 



" Yours sincerely, 



" A. HANNAY. 



"Kirkcudbright, 18th Nov. 1841." 



" Invershin, Bonar Bridge, Aug. 9th, 1852. 

 " My dear sir, I duly received your favour of the 3rd instant, 

 and will be always happy to hear from you. You are right with 

 regard to the time the salmon-fry remain in the river after 



