A GOLD _MINE. 71
of the earth. Without iron and steel mankind does not advance above barbarism. To conquer the material world he must have tools and machinery. Without metals mankind could neither make a conquest of material nature nor extricate himself from the lower brute stratum of life, and without the metals brought together in veins it would be impossible to obtain them. Thus, On small hinges turn great doors." All veins mark the places of rents or cracks in the rocks ; no matter whether they are great fissure veins many miles in length, and from ten to two or three hundred feet in width in places, or whether they are only a few feet in length and thinner than a knife blade, the origin is the same ; they are healed rents.
For the most part, over all the earth this mending or healing the wound is done with silica or quartz. This is a very common mineral, entering largely into the composition of almost all kinds of rocks. It is one of nature's main materials used in the construction of this earth. When analyzed by a chemist it is found to be made of two elements, namely, oxygen, on which we depend for the breath of life, and silicon, a metal never found outside of the clutches of this terrible oxygen. They are interlocked in an embrace that was formed when the earth was