408 Fisuinc 1x AmericAN WATERS. 
question which has been agitating the minds of the most en- 
lightened pisciewturists of the age for years has been, How 
we can best contrive that the fish shall have a free passage 
up the rivers, in order to continue its species without any loss 
of water-power or profits on the part of the mill-owners? If 
we can show them that this is possible, we have a natural 
right to compel those who have blocked up our rivers for 
their own profit to give the fish a free passage as a public 
benefit. The very best passage through a dam is an open 
run by means of a good wide pass in the centre of the dam, 
or, at any rate, in such part of it as will easily be found by 
the salmon, in showers, when the water-power is generally 
more than enough for the requirements of the mill and fhe- 
tory. There can be no great difficulty about this (proper re- 
gard, of course, being paid to the stability of the dam), ex- 
cept on rivers where the power is at all deficient, when con- 
trivances, such as ladders, ete., ete., are needed to prevent the 
waste of any of the water-power. It is true that salmon can 
jump up a fall of considerable height. Indeed, salmon have 
been known to partly jump and partly swim up falls of ten 
or twelve feet in height, and even much more; but the ca- 
pability requires certain conditions for its performance, and 
chief of all these is a good deep pool at the foot of the fall 
or dam as a starting-place, and the more arched or slanting 
out of the perpendicular the fall is, the easier the salmon will 
surmount it. It used formerly to be supposed that a salmon 
jumped out of the water in the way that mites ane seen to 
jump in a rotten cheese, viz., by putting the tail to the mouth, 
and then, by the exertion of a sudden effort of muscular ex- 
pansion, forcing its broad tail to act upon the water so as to 
shoot the fish ahead. This is now known to be fallacious, as 
it is seen that the salmon is quite powerless to leap any dam 
when the waters at the foot of the dam are shallow; and it 
is known that salmon leap like all other animals (except 
cheese-mites), viz., by acquiring the utmost attainable veloc- 
ity by means of a run, and then, by a sudden and powerful 
