Let us trace one of these and discover the giant. We hike, or ride a sure-footed horse, six miles up one of the somber gashes in the mountains, called cañons, arriving at the origin of a stream we have seen growing smaller as we ascended. We find a little spring gushing from beneath a huge boulder and trickling down through the ferns and brush. Soon it is joined by other little streams on the right or left. Presently, as we stumble along down the rocky trail, we see on one side a wide, deep gulch, with walls of sandstone or granite rising almost perpendicularly on either side. And that gulch has snow lying in it, perhaps forty feet deep--the drifts of last winter or slides from the slopes above it. The snow may then have been sixty or a hundred feet deep, but now, in midsummer, it is dwindling fast, and its water doubles or triples the size of our little stream. Suddenly we see that the wild, rocky, torrent bed has been cleaned out, and that the banks are lined up with rock. The genie has been giving orders. A few rods farther that torrent bed gives place to a timber flume; and the next moment that flume, instead of keeping on the sharply sloping floor of the cañon, rises on trestles, holding an almost level position. The trestle increases in height as the ground beneath them slopes downward, and cross a deep gulch, still holding the little torrent running between the wooden walls of the flume. From our trail beneath we see the flume now skirting round the waist of some stupendous mountain, then crossing other gulches, and soon appearing on the summit of a peak, eight hundred feet above where we are standing. Below, at the foot of that peak, is a small, plain, stone building, and, wriggling down from the summit, is, apparently, a huge black snake, poking its nose into the basement of that house. The house holds the generators for turning the force of that torrent into electricity. The snake is the penstock--a great black steel pipe, twisting and turning to avoid the huge boulders in its path as it conducts that water from the summit into the turbines in the house. The turbine is an enclosed water-wheel in which every particle of force in the rushing water is used to turn a great steel shaft. On the other end of that shaft is geared the generator--the wonderful machine with wire-wound arms which makes the electric current. At this particular power-house the little torrent which reaches the summit in a flume thirty inches wide and two feet deep turns out 800 horse-power. It is the force, not the size, of the stream which gives that power, for water has a pressure of about fifty pounds per square inch for every hundred feet of the height of its source. So this water has a pressure at the turbine of four hundred pounds per square inch--a far greater pressure than that in the cylinders of a great Mogul mountain locomotive.