Without the prospector there would be no mining and the world would yet be in the stone age. He is not appreciated at anything like his real worth. He requires ability and experience, push and perseverance. Prospecting is a search for valuable minerals. He may not be very deeply learned in either geology or mineralogy, but he must have a keen eye and good natural powers of observation. There are some sixty or seventy elements in the world, and the most common is oxygen. Nearly all the coloring matter of rocks comes from iron. Wind, frost, rain, snow, and heat, cause a crumbling of the different rocks, and running water wears them away, and carries off and distributes the particles. By this agency, and by floating ice, they are often removed to long distances. The action of internal heat renews the deposits of mineral by eruption, or by hot springs, but this means of renewal was much more powerful in the past than it is now. Organic matter found in the crust of the earth was derived from animals or vegetables. Coal is a legacy from forests that flourished ages ago, while petroleum is all that remains of vast schools of fishes that swarmed in Devonian seas. Stratified rocks are either sand, clay, or calcareous, which means lime-bearing. In their natural position they were horizontal, but owing to subsequent volcanic action they are, in some localities, tilted at all conceivable angles. The eruptive rocks have burst through them in places, changed their character, divided them by intrusive masses, and generally enriched them with mineral deposits. Everything now known points to the theory that the contents of veins were deposited in the lodes by infiltration. In a few instances famous mines have no veins, but are literally hills of mineral; they are then of low grade, but much more remunerative than average high grade mines, owing the vast quantity of ore, and the ease with which it can be mined. The famous Treadwell mine, on Douglas Island, Alaska, has ore that is worth less than four dollars a ton, but it is quarried, and 640 stamps work day and night. There is about a dollar a ton profit, and hundreds of thousands of tons are treated annually. The tin mine known as Mount Bischoff, in Tasmania, and the Burra copper mine in Australia are other instances. Each of these deposits was found as an outcropping on the bare top of a low hill, and none of them has walls. A fault may throw the vein up or down, and a good deal of exploration may have to be done before it is recovered. A lenticular vein consists of a series of double pointed ore bodies like lenses which may be strung out, overlapping, or not. The outcrop of a vein is never the same as its strike, except on a level surface. A stringer of ore branching off from the main vein is known as a chute, shoot, or chimney.