Even birds of active flight frequently come to grief upon the wires.

In December 1906, near Innerwick, a large flock of Golden Plover was observed to fly before a strong wind against telegraph wires, seventeen in number, with the result that thirty-one of the birds were killed.

In rivers as well as on land, the advances of civili- zation have told hardly upon the original inhabitants.

The erection of mills for the manufacture of woollen and linen cloth, of flour, meal and paper, and the construction of dams ,to obtain the necessary " head " of water to drive the machinery, have given rise on almost every stream to barriers which have interfered with the free passage of the smaller organisms of the waters, and have in some cases seriously checked the movements of even the large migra- tory fishes.

This effect was clearly shown in America where the erection of mills and their dams on the Connecticut River greatly diminished the number of migrating Salmon, though in this case a compensating increase of other fishes was the result, for the Striped Bass on which the Salmon fed, multiplied as their destroyers disappeared.