138 THE LIFE OF THE SALMON 



not greatly different, except possibly at the extreme 

 upper ends. When, however, the fish essay to 

 ascend farther, they are met by distinctly colder 

 water, and their progress is at once checked, till, the 

 particular time when the winter conditions of those 

 upper rivers having passed, they find themselves 

 once more wilhng to travel and overcome obstacles 

 in their course. The rivers Garry and Orch^'- are 

 the early rivers of their districts, therefore, because 

 all the lower waters are of such a relatively high 

 temperature as induces rapid ascent, while the Garry 

 and Orchy are of a temperature which in Scotland 

 produces a check upon early ascent. Added to this 

 we must not forget that small falls exist in each 

 case. Spring fish are no jumpers till summer con- 

 ditions have come about. 



Apply this interpretation to the Tay and its upper 

 water, the Dochart, and we see that while the main 

 river, with its course of some 50 miles, receives 

 various large tributaries, and has a general tempera- 

 ture in the first four months of the year which at 

 times induces fish to run and at times checks their 

 running, thus naturally securing to this fine river a 

 distribution of spring fish, the Dochart — which has 

 a fall upon it a short distance above Loch Tay — is 

 exactly analogous to the waters of the Garry or 

 Orchy above their respective falls. Fish therefore, 

 if we argue by analogy, should, as in the Garry and 

 Orchy, ascend the Dochart fall when the wintry 

 conditions have passed. This is, as a matter of fact, 

 exactly what happens, for the Loch Tay fish begin 

 to go up the Dochart in May, 



