Surroundings have quicker and stronger effect on collies than on almost any other kind of dog.

And these surroundings, very evidently, were not to the collie's taste.
Several times, when the path's width permitted, he dropped back to Gavin's side, to receive a word of friendly encouragement or a pat on the head.
Outside of the grove's shadows the sun was sinking.

Not with the glowing deliberation of sunsets in northern latitudes, but with almost indecent haste.

In the dense shade of the forest, twilight had fallen.

But the path still lay clear.