About the best advice that can be given to a man who has determined to go to some out of the way region where there is a possibility of his discovering minerals is to recommend him to visit the nearest museum and gain an acquaintance with the common rocks. Should he be unable to do this he had better provide himself with small, inexpensive specimens from the shop of some dealer. It is almost impossible to teach a beginner to distinguish the various rocks by any amount of printed instruction; the only way to learn to recognize them is to handle them and note carefully their color, weight, and the minerals that go to make them up. The explorer should be able to recognize at a glance, or at any rate after a very short inspection, the sedimentary rocks, such as sandstone and limestone; the metamorphic rocks, that is, rocks that have been altered by the agency of great subterranean heat in ages long past, and which were probably stratified rocks at one period, such as granite and gneiss, and the truly igneous rocks--trap, diabase, diorite, etc. He must know also that mysterious rock which the western miner calls porphyry, and to which is ascribed most wonderful virtues in the way of ore attraction; while dolerite and dolomite must be to him familiar terms and substances. This sounds easy enough but the student will find that a good deal of hard work is necessary before he can readily recognize each of these rocks. It is even more necessary that he should learn the metals thoroughly. Each one differs from all the rest in some particular. Often this difference will be an obscure one, but to the careful investigator the recognition of the substance will be in the end certain. They may differ in weight, in color, in hardness, in a dozen different ways, so that to the man who has made a study of this subject a determination is always possible.