Mohave County miner., 1915-03-27

to an anlmaCeQ QlScuSSlOn, pracClcally all of which ran in favor of the views which he had advanced.
 In 1900 interest in the subject was was again aroused by the presentation to the American Institute of Mining Engineers of another paper by Prof. c. R. Van Hise, entitled "Some Princi- ples Governing the Deposition of Ores. The subject of cavities in rocks receiv- ed careful attention. The depth to which cavities can maintain themselves beneath the ever accommodating load of superincumbent rock had been calcu- lated by a colleague, Prof. Hoskins. It was placed at somewhere about l0,- 900 millimeters. Water, practically all from the rainfall, was believed to extend down to the limit of cavities; to pass through extended masses of rock, wandering more or less laterally; and after taking into solution the minerals of ores and gangue, and after absorb ing much heat because of the normal increase of temperature with depth, to rise again to the upper world, deposit ing the vein filling in its passage. Three zones were established: zone or belt of weathering or solution, cor responding to the vadose zone of Posep- ny; zone of enrichment on or near the water level and zone of cemen- tation or precipitation at great depth. These views were verified by many ex- amples and were presented in a way that carried almost universal convic- tion. We may say that they marked the high tide of the views dependent upon rain waters, often called the me- teoric waters, as agents in the pro- duction of veins. From them we may now turn to the development of others of contrasted nature, and then to certain limitations to which the views dependent upon the rain waters are subject.
 Early in the nineties readers of the literature on this subject began to be impressed with the valuable contribu- tions from Prof. J. H. L Vogt of Christiana, Norway. In the first vol ume of the Zeitschrift fur Parktische Geologic, Prof. Vogt published series of papers embracing views which he had gradually developed by years of study in Norway. They relate partly to the basic masses which we find in igneous rocks, such as the titaniferous iron ores, which are direct crystalliza- tions from molten magma; partly to the border effects of igneous masses, effects which were believed to be due to emissions from the igneous rock. In the latter group come the pegmatites with their contents of rare earths; the tin ores associated with quartz, fields par and mica; and apatite deposits in close connection with intrusive masses of gabbro. These deposits Prof. Vogt called "pneumatolitic" when produced by vadoes in connection with liquid water.
 The first papers of Prof. Vogt have been followed by long series since then. The ideas suggested were also germinating in the minds of others on this side of the water. We find in the monographs of J. E. Spur, on Aspen and on Mercur, the conclusions that the ores were derived from some deep- seated mass of igneous rock. During these years in the decade of the nine- ties, we all began to think there must be something in the waters which might be derived from crystallizing bodies of molten and cooling masses. Some of us were also wondering whether the meteoric waters quite met all the re- quirements of the case.
 At the meeting of the American h. stitute of Mining Engineers, held in Richmond in 1901, made the point that the deep mines, which were rapid ly multiplying in various places the world over, passed through zone of water-bearing rocks, and if the water were impounded in the upper levels, their lower workings were practically or actually dry. There were indeed one or two regions of expiring igneous