A rolling park extended as far as Helen could see, bordered by forest that in places sent out straggling stretches of trees.

Here and there, like islands, were isolated patches of timber.
At ten thousand feet elevation the twilight of this clear and cold night was a rich and rare atmospheric effect.

It looked as if it was seen through perfectly clear smoked glass.

Objects were singularly visible, even at long range, and seemed magnified.

In the west, where the afterglow of sunset lingered over the dark, ragged, spruce-speared horizon-line, there was such a transparent golden line melting into vivid star-fired blue that Helen could only gaze and gaze in wondering admiration.
Dale spurred his horse into a lope and the spirited mounts of the girls kept up with him.