A number of mountain streams and rivers in the Yosemite deliberately make their way to the brink of a vast gorge that has its brow in the sky, and there, in full self-control, they plunge over.
Jutting rocks, and smooth steep inclines throw streams into wild, uncontrolled excitement. But where a vertical river drops its fluttering current against a magnificent mountain-wall, everything is harmonious and controlled, and the stream appears to have the sublime composure of a Big Tree.
In a stream-channel water goes forward with crowding intermittent rushes. These, in plunging over a brink, break up into numerous closely falling rockets or comet-like masses, each tailed with spray. These in turn separate and divide into other such masses, with spray and water-dust.
In a drop of several hundred feet a mass of water is likely to expand to several times its width at the brink. This expansion varies with the volume of water, the height of the drop, and the direction and speed of resisting wind-currents.
Swaying and bending are further attractions of waterfalls. Bridal Veil Falls often swings and sways gently from side to side. This movement is sometimes accompanied by lacy flutterings at one or more places on the spray-wreathed white fall. Numerous falls in the Yosemite are high and spread widely in descending, and frequently the fall dances splendidly as its white, airy mass keeps time to the changing movements of the wind.
Many of these high falls are accompanied at times by a fluttering of numerous rainbows. These flaunt, shift, and dart like great hummingbirds. At the Lower Yosemite, Bridal Veil, and Vernal Falls these rainbows sometimes momentarily form a complete circle of color. By these, too, the moon produces similar though softer, stranger effects. Perhaps the most pleasing, delicate, and novel effects in lunar rainbows are to be had about the foot of Yosemite Falls.
The slender Ribbon Fall has a vertical drop of twenty-three hundred feet; the Upper Yosemite, about sixteen hundred feet. Nevada Falls is about six hundred feet high. Vernal Falls is one hundred feet wide at the top and drops three hundred feet. The Vernal and Nevada Falls are in the midst of magnificent and novel rock scenery. The Illilouette Fall is about six hundred feet high and is one of the most beautiful in the Park.
The Tueeulala and Wapama Falls in Hetch-Hetchy have their own individual setting and behavior. The Wapama, though lacking the verticality of the Upper Yosemite Falls, carries a greater volume of water. Yosemite Creek is a true mountain stream. In its first ten miles it goes through a number of zones, passes a variety of plant life, and makes a descent of six thousand feet. One third of this descent is in the Falls of the Yosemite.
John Muir tells us that one windy day the Upper Falls was struck by an upward wind pressure that bent and drove the water back over the brow of the cliff. The wind held back the water so that the fall was cut entirely in two for a few minutes. But more wonderful than this was one day when the wind struck the Upper Falls at a point about halfway down and there stopped and supported its falling waters. For more than a minute the water piled up in an enormous conical accumulation about seven hundred feet high. All the while the water poured over steadily from above, and the entire mass rested upon the elastic but invisible air. Then came a wild collapse.