92 NATURAL HISTORY OF THE SALMON. 



but the marking of two or three hundred 

 thousand fish is a difficult process, seeing they 

 leave the pond in such immense shoals; how- 

 ever, undoubtedly many more might have been 

 marked, if more hands had been employed to do 

 it. One great difficulty in marking is, the shoals 

 generally leave during the night: it is true the 

 sluice, which is always open, might have been 

 kept shut during that time, and only opened 

 during the day; but we would not approve of 

 keeping back the fish at any time when willing 

 to go. We understand Mr Buist is to arrange 

 for as many as possible being marked this 

 spring. 



The experiment, also, has proved that the 

 marked grilse of one year return as salmon the 

 next; and we think it has also proved that all 

 the smoults of one year do not return the same 

 year as grilse, the one-half returning next spring 

 and summer as small salmon. This idea was first 

 suggested by a correspondent in the Perthshire 

 Courier, who says, "That the habit of the salmon 

 species, in adopting a double or divided migra- 

 tion to the sea as smoults and from the sea in 

 their later stages, has only been known within 

 these few years. It was discovered, in regard to 



