224 THE SALMON. 



obvious that salmon ab ovo, and before that, up to the 

 age of puberty, are, in their natural abodes, exposed to 

 very great perils, the chief of which may be classed as 

 preventible. Thus, there is enormous loss by spawn 

 being deposited during floods, when the rivers are high, 

 in positions where, when the waters fall, it is destroyed 

 by frosts or drought, or trampled under foot of man and 

 beast ; an evil of late very greatly increased by the ex- 

 tension of land drainage, especially the hill or open drain- 

 age, which causes the rivers both to rise higher and to 

 sink lower and more rapidly. Then great quantities of 

 the ova are devoured by fish and birds ; and after the 

 fish are hatched, their dangers from other sources, up to 

 the period of their seaward emigration, are still greater. 

 These and sundry other evils can be avoided, to a great 

 extent, by semi-domestic rearing ; the eggs can be pre- 

 served from accident, and the young kept separate from 

 their natural enemies until the time comes when they 

 themselves think they have sufficient strength and know- 

 ledge to seek their fortunes abroad. The extent to which 

 the preventible evils operate, and to which they may be 

 cured, cannot be stated with precision, but enough is 

 known to indicate, with considerable certainty, that a 

 very considerable work of restoration may be accom- 

 plished. Sir Humphry Davy's estimate was that, on the 

 average, each salmon deposits 17,000 eggs, of which only 

 800 come to perfection ; and although even his authority 

 on such a point is not decisive, we have nothing better. 

 Then as to the destruction from various causes that takes 

 place after the hatching, we may form, though not an 

 arithmetically accurate, a sufficiently clear and large idea, 



