ed for the purpose, and in the
ensuing months of June and July he recaptured a considerable number on
their return to the rivers, all in the condition of grilse, and varying
from 3lbs. to 8lbs., "according to the time which had elapsed since
their first departure from the fresh water, or, in other words, the
length of their sojourn in the sea." In the spring of 1842, he likewise
marked a number of descending smolts, by clipping off what is called the
adipose fin upon the back. In the course of the ensuing June and July,
he caught them returning up the river, bearing his peculiar mark, and
agreeing with those of 1837 both in respect to size, and the relation
which that size bore to the lapse of time.

The following list from Mr Young's note-book, affords a few examples of
the rate of growth:--

_List of Smolts marked in the River, and recaptured as Grilse on their
first ascent from the Sea._

Period of marking. | Period of recapture. | Weight when retaken.
---------------------+----------------------+----------------------
1842. April and May. | 1842. June 28. | 4 lb.
... ... | July 15. | 5 lb
... ... | ... 15. | 5 lb.
... ... | ... 25. | 7 lb.[18]
... ... | ... 25. | 5 lb.
... ... | ... 30. | 3-1/2 lb.[18]

We may now proceed to consider the final change,--that of the grilse
into the adult salmon. We have just seen that smolts return to the
rivers as grilse, (of the weights above noted,) during the summer and
autumn of the same season in which they had descended for the first time
to the sea. Such as seek the rivers in the earlier part of summer are of
small size, because they have sojourned for but a short time in the
sea:--such as abide in the sea till autumn, attain of course a larger
size. But it appears to be an established, though till now an unknown
fact, that with the exception of the early state of parr, in which the
growth has been shown to be extremely slow, salmon actually never do
grow in fresh water at all, either as grilse or in the adult state. All
their growth in these two most important later stages, takes place
during their sojourn in the sea. "Not only," says Mr Young, "is this the
case, but I have also ascertained that they actually decrease in
dimensions after entering the river, and that the higher they ascend the
more they de