agencies and processes whose action has accomplished the changes. Such a comprehensive science has naturally developed special aspects or subdivisions, the following being those usually recognized: Cosmic or astronomic geology, which treats of the relation of the earth to the universe in general and to the solar system in particular the external relations of the earth. Geognosy, which treats of the matter constituting the earth. and its arrangement. As subdivisions of geognosy we have: (a) Mineralogy which treats of minerals the chemical combinations in which the elements constituting the earth's crust are found in nature. (b) Petrology, which treats of rocks i.e., the aggregates of different composition and structure in which the minerals are found in the accessible part of the earth's crust. Structural or geotectonic geology, which treats of the structural arrangement of the earth's material the "architecture of the earth." Physiographic geology, which treats of the surface features and changes of the same the topography of the earth's surface. Paleontology, which is concerned with the fossils or remains and traces of plant and animal life found in the rocks. Historical geology, which attempts to give an account of the succession of events through which the earth's surface has passed. Stratigraphic geology, which is a study of the succession of the beds of rock laid down during the progress of the geologic ages. This succession is worked out in part by the aid of the science of paleontology. Dynamic geology, which discusses the causes, agencies, and processes that have operated or are operating on the earth. Economic geology, which deals with the applications of the science of geology in industrial relations and operations. Mining geology, which is a subdivision of economic geology concerned with the application of geologic facts and principles to mining. If the terms, medical jurisprudence, dental jurisprudence, legal chemistry, law of literature, etc., are justifiable, then it seems that it is also justifiable to use the term, Legal geology, which deals with the application in litigation of the facts and principles of geology, particularly its subdivisions, mineralogy, economic geology, and mining geology. Legal geology is the subject-matter of this treatise in the same way that certain applications of medical facts and principles in litigation form the subject-matter of the various treatises on medical jurisprudence; but, in order that the title of the book shall adequately represent its contents to the average man who will probably have occasion to use the same, I have, instead of entitling it "Legal Geology," used the phrase "Mining, Mineral, and Geological Law." This gives adequate prominence to the subdivisions of geology that have given rise to by far the larger part of the law relating to subjects included in geology when this word is used in its widest sense. Any further attempt even to outline the subject of general geology in this book would be unadvisable, for the space that could be allotted would be so limited that it would be useless for any practical purpose. It has seemed to me much the better plan to give in a bibliography (see Appendix) the titles, together with a brief description and appraisal, of the many excellent books, both on general geology and on its several subdivisions that are in print, so that any person searching for any variety of geologic information may know in what book or other publication it is to be found. On two of the topics of economic geology, ore deposits and veins, which are so intimately related to the legal use of geology, I have ventured to give a brief outline of the present state of the science: first, because of their direct and exceedingly important application in American mining laws; and, second, because as yet most of the literature on these subjects is only to be found in the "proceedings" of scientific associations or in the files of special periodicals usually inaccessible to the general reader. Among the other sciences sometimes involved in mining litigation mention should be made of: Analytical chemistry, which treats of the methods of determining the elements and their combinations and the amounts thereof present in any substance. The determination of the amounts of the precious metals present in an ore is usually termed Assaying, which is also, but less accurately, applied to the determination of the amounts of lead, tin, zinc, and copper in their ores. Assaying is carried out in two ways: (1) Fire assays, in which by treatment of the ore in a furnace the metal is obtained in the form of a small globule or "button," which is weighed on a delicate balance. This method is chiefly used for the estimation of gold and silver. (2) Wet assays, in which the ore is dissolved by acids or other reagents and the metals are precipitated therefrom as chemical compounds, which are either dried and weighed, or the amount of metal is determined directly in the solution by titration, called the "volumetric" method. The latter process is described in books on analytical chemistry. It must always be remembered that while the methods of analytical chemistry are very accurate and, when carried out by competent men, the results are entirely trustworthy, the amounts of ore or other substance that can be treated and the metal actually separated and weighed are relatively very minute, usually only the fraction of an ounce. Consequently, in order that the metal may be present in the very small sample that is analyzed or assayed`in exactly the same proportion that it exists in carload lots of ore, or in an ore-body exposed in a shaft, drift, stope or other mine opening, the utmost care in sampling must be exercised, otherwise the most accurate analytical results will be worthless. It is as important to have the sampling accurately and properly done as it is that the chemist or assayer understand his profession.2 2 A practical method of assaying or testing ore in the field for silver and gold is a matter of much interest to prospectors and engineers; for usually the appearance of an ore, not only does not give any clue to its richness, but does not even tell whether it contains the precious metals at all. The best methods that have been proposed for this purpose are the following: 1. The ore (after roasting over an open fire, if a sulphide) is crushed and triturated in an iron mortar with mercury; the mercury collected by panning and driven off by heat. The gold and silver remaining may be weighed on a small pocket balance. A. I. M. E., vol. xxv, p. 645; vol. xxvi, p. 187. 2. A bead of the metal is obtained by scorification and cupellation by the blowpipe. This is measured by a microscope provided with an eyepiece micrometer, and the weight obtained by a table from the observed diameter. Luther Wagoner, A. I. M. E., vol. xxxi, p. 798; J. S. Curtis, Annual Report U. S. Geological Survey, 6th. 3. A bead is obtained by the blowpipe as in method No. 2, and its diameter measured, either by means of the Plattner ivory scale or by the Richards aluminum scale, and the weight obtained from a table of diameters. J. W. Richards, Jour. Am. Chem. Soc., vol. xxiii, p. 203. The objection to the first method is the weight of the necessary apparatus and the inaccuracy of the results, owing to the fact that amalgamation with mercury will not extract all the gold and silver. The writer has tested methods 2 and 3 in the assay laboratory of the Columbia School of Mines SCIENTIFIC DEFINITION OF A MINERAL From the scientific standpoint, a mineral may be defined as an inorganic, homogeneous substance of a definite or approximately definite chemical composition found in nature and having certain distinguishing physical characteristics. If formed under FIG. 1. Example of igneous rock in thin section as From micro-photograph by C. H. Shamel. suitable conditions, it also has a definite molecular structure. which is exhibited externally in its crystalline form and internally in its cleavage, its behavior with respect to light, etc. It also and finds that both give good results. Measurement by the microscope gives results agreeing very closely with those obtained by weighing the beads on the best assay balances. The Richards aluminum scale is much superior to the old Plattner scale. The results obtained by the former, while not so extremely accurate as by the microscope, are all that can be asked for testing ores in the field. Of course none of these methods can replace the regular fire assay for the accurate determination of the gold and silver contents of large ore-bodies or mine samples; but they are nevertheless very useful in field work for the testing and approximate assay of gold and silver ores. The best book on quantitative assaying with the blowpipe is Fletcher's, mentioned in the Bibliography. possesses certain other properties such as specific gravity, hardness, fracture, tenacity, luster, color, fusibility, etc. All of these or only some of them may belong to a mineral which is amorphous, that is, not crystallized. The behavior of minerals toward polarized light is the foundation of the modern science of petrology. Thin sections of rock are ground, and when examined by a polarizing microscope, all the minerals that go to make up the rock can be identified, thus furnishing the basis for the accurate FIG. 2. Example of igneous rock in thin section as seen through a petrographic microscope; quartz diorite from Schwartzenburg, Germany, showing plagioclase feldspar, quartz, hornblende and magnetite. Magnified 30 diameters. From micro-photograph by C. H. Shamel. classification and identification of rocks. This is particularly valuable in the case of the igneous and metamorphic rocks and of the mixtures of minerals that form the contents of veins or make up ore-bodies. These questions of the identity of rocks or mineral bodies often become of the utmost practical importance in litigation, particularly that concerning extralateral rights, as well as invaluable guides in prospecting and the development of mines. The science of petrology, as based on the microscopic miner |