alone has taken place, the prevailing form of the valleys is that of the U-shaped.  Yosemite approximates to this shape, and ice has certainly played a part in its formation.  But the glacier seems to have stopped at the outlet of the great valley; it did not travel beyond the gigantic hall it had helped to excavate.  The valley of the Merced from the mouth of Yosemite downward is an open valley strewn with huge angular granite rocks and shows no signs of glaciation whatever.  The reason of this abruptness is quite beyond my ken.  It is to me a plausible theory that when the granite that forms the Sierra was lifted or squeezed up by the shrinking of the earth, large fissures and crevasses may have occurred, and that Yosemite and kindred valleys may be the result of the action of water and ice in enlarging these original chasms.  Little wonder that the earlier geologists, such as Whitney, were led to attribute the exceptional character of these valleys to exceptional and extraordinary agents—­to sudden faulting or dislocation of the earth’s crust.  But geologists are becoming more and more loath to call in the cataclysmal to explain any feature of the topography of the land.  Not to the thunder or the lightning, to earthquake or volcano, to the forces of upheaval or dislocation, but to the still, small voice of the rain and the winds, of the frost and the snow,—­the gentle forces now and here active all about us, carving the valleys and reducing the mountains, and changing the courses of rivers,—­to these, as Lyell taught us, we are to look in nine cases out of ten, yes, in ninety-nine out of a hundred, to account for the configuration of the continents.

The geologists of our day, while not agreeing as to the amount of work done respectively by ice and water, yet agree that to the latter the larger proportion of the excavation is to be ascribed.  At any rate between them both they have turned out one of the most beautiful and stupendous pieces of mountain carving to be found upon the earth.

IV

THROUGH THE EYES OF THE GEOLOGIST

I

How habitually we go about over the surface of the earth, delving it or cultivating it or leveling it, without thinking that it has not always been as we now find it, that the mountains were not always mountains, nor the valleys always valleys, nor the plains always plains, nor the sand always sand, nor the clay always clay.  Our experience goes but a little way in such matters.  Such a thought takes us from human time to God’s time, from the horizon of place and years to the horizon of geologic ages.  We go about our little affairs in the world, sowing and reaping and building and journeying, like children playing through the halls of their ancestors, without pausing to ask how these things all came about.  We do not reflect upon the age of our fields any more than we do upon the size of the globe under our feet:  when we become curious about such matters and look upon the mountains as either old or young, or as the subjects of birth, growth, and decay, then we are unconscious geologists.  It is to our interest in such things that geology appeals and it is this interest that it stimulates and guides.