He felt the horse plunge down, there was a shock, and he was flung violently from the saddle.

He struck a precipitous slope and rolled down it, clutching at twigs, which broke, and grass, until he felt a violent blow on his head.

After that he knew nothing.
It was broad daylight when consciousness returned, and he found himself lying half-way down a steep declivity.

At the foot of it tall reeds and sedges indicated the presence of water, and he realized that he had fallen into a ravine.

There was a small tree near by, against which he supposed he had struck his head; but somewhat to his astonishment he could not see his horse.