"It is sufficient to say that the first examinations are made by passing over the ground with the compass in a northwest and southwest direction, at intervals of a few rods, until indications of ore are found. Then the ground should be examined more carefully by crossing the line of attraction at intervals of a few feet, and marking the points upon which observations have been made, and recording the amount of attraction. Observations with the ordinary compass should be made, and the variation of the horizontal needle be noted. In this way materials may soon be accumulated for staking out the line of attraction, or for constructing a map for study or reference. "After sufficient exploration with the magnetic needle, it still remains to prove the value of the vein by uncovering the ore, examining its quality, measuring the size of the vein, and estimating the cost of mining and marketing it. Uncovering should first be done in trenches dug across the line of attraction, and carried quite down to the rock. When the ore is in this way proved to be of value regular mining may begin. In places where there are offsets in the ore, or where it has been subject to bends, folds, or other irregularities, so that the miner is at fault in what direction to proceed, explorations may be made with the diamond drill." CHAPTER II. HOW TO TEST FOR MINERALS. When the mineralogist wishes to know the names of the specimen he holds in his hand, he, in the case of a mineral difficult to determine, considers all the following properties: Crystalline form and structure, Cleavage, Fracture, Tenacity, Hardness, Specific Gravity as compared with that of water, Luster, Color and Streak, Transparency or otherwise, Taste, Odor, Chemical Composition tested by analysis, Pyrognostic characters as determined by the use of the blowpipe, Mode of occurrence and associated minerals. Crystalline Form and Structure. Unfortunately the science of crystallography is extremely complicated and long study is necessary to master it; once acquired, however, it is of paramount usefulness to the student. According to Dana there are six systems, to one of which every crystal may be referred. They are: (1) Isometric; (2) Tetragonal; (3) Hexagonal or Rhombohedral; (4) Orthorhombic; (5) Monoclinic; (6) Triclinic. In the isometric system there are three equal axes at right angles to each other. In the tetragonal system there are three axes at right angles to each other. Two of these are equal, while the third, or vertical angle, is longer or shorter.