It is also known that superheated steam suddenly takes on such great power that no boiler can hold it. Once let the water in a boiler get very low and no boiler can hold the force of the resultant superheated steam. The same heat that, applied to water, gives perfect safety, applied to steam gives utter destruction. Hence the amazing force of the vast jets of the geyser that follow the first spurts. As soon as the steam is blown off the subterranean waterworks fill the tube and the process is repeated. This modus operandi was first proposed as a theory by Bunsen in 1846, and later was demonstrated by the artificial geyser of Professor J. H. J. Muller, of Freiburg. [Illustration: Pulpit Terrace and Bunsen Peak.] MOUNDS OF MINERAL DEPOSITS I have the extremely difficult task of representing emotions by words--glories of color and form seen by the eye by symbols meant to be addressed to the ear. Before seeking to describe the diverse colors made largely by one substance, let us remember that while silica, the principal part of these water-built mounds, is one of the three parts of granite, namely, the white crystal quartz, it is also the substance of the beautifully variegated jasper, the lapis lazuli, the green malachite, and the opal, with its cloudy milk-whiteness through which flashes its heart of fire. Silica and alumina combine to make common clay, but alumina forms itself into the red ruby, the golden-tinted topaz, the violet oriental amethyst, the red, white, yellow, and violet sapphire, and the beautiful green emerald. With substances of such rare capabilities we may expect rich results in color and form. We turn now to deposits from water of these two substances, especially the first. About the Old Faithful geyser is a mound about one hundred and forty-five feet broad at the base, twelve feet high, jeweled over with pools of beauty of every shape, beaded and fretted with glories of color never seen before except in the sky. How were they made? Water is a general solvent. It can take into its substance several similar bulks of other substances without greatly increasing its own, some actually diminishing it. Hot alkaline water will dissolve even silica rock. When water is saturated with sugar, salt, or other substance, if a little or much water is evaporated some of the saturating substance must be deposited as a solid. All crystals, as quartz or diamonds, have been made by deposits from water. Hot water can hold in solution much more of a solid than cold water. Therefore, when hot water comes out of the earth and is cooled, some of the saturating substance must be deposited as a solid. It is done in various ways, especially two.