8 
When salmon are swimming in the river Tweed up 
stream, it has been estimated by experienced anglers that 
they travel at the rate of about two miles per hour. 
Salmon, in descending the river after spawning, are 
generally emaciated and exhausted. Many, apparently 
hardly able to swim, float down the stream to the sea. 
Every spring, large numbers are found dead at the sides 
of the river, or in pools. 
What causes the migration of salmon is matter of con- 
jecture. I have observed, when walking along the Ber- 
wickshire coast, salmon leaping frequently at or near the 
mouths of small rivers or streams; and it has occurred to 
me that, as they must get into rivers for spawning, instinct 
induces them to seek those rivers the waters of which they 
find most suitable for the purpose. 
Certain it is that salmon, after having frequented 
particular rivers from time immemorial, have abandoned 
them, and the inference is that they betake themselves to 
other rivers which they deem preferable. | 
As an example of this, I may refer to the river Whit- 
adder, which has a course of about forty miles from the 
Lammermuir Hills. This river joins the Tweed, at a dis- 
tance from its mouth of about three miles; so that all 
the salmon caught in the higher parts of the Tweed must 
have passed the mouth of the Whitadder. The tide flows 
into it, as well as into the Tweed, flowing up the latter, 
for six or seven miles. Formerly the true Salmo salar 
frequented the Whitadder; but during the last thirty 
years no salmon of that variety has been seen init. It 
is frequented only by bull-trout. 
Reference may also be made to the Thames and to the 
Coquet (Northumberland), both of which rivers used to be 
frequented by the true salmon. I might also quote the 
