of the principles and conditions governing the origin, movement, and segregation of oil and gas, thus extending direct aid in the discovery of new pools and new fields. With this object in view, attention is given not only to the geologic structure in the pools already developed and to the mutual relations of the oil, gas, and water as revealed by the drill, but to the problems of discontinuity, tightness, cementation by chemical reaction, porosity, and the more difficult questions of capillarity. In the investigations of such subjects, concerning which some misinformation seems to exist, the physicists of the division of chemistry and physics are cooperating with the geologists.

Estimates of the reserves of petroleum remaining in the ground in the different States were compiled in February by the Survey geologists for the use of the Secretary of the Interior in reply (Senate Doc. 310) to Senate resolution No. 40, Sixty-fourth Congress. Further, in anticipation of the day when, on account of the advancing cost of gasoline and other products obtained from petroleum, it might be found commercially profitable to utilize some of the enormous supply of petroleum to be derived from the distillation of the vast deposits of so-called hydrocarbon shales of the Green River formation of northwestern Colorado and northeastern Utah, the Survey has for three years been making field investigations of these deposits. The examinations have been accompanied by mapping of the areas of hydrocarbon shales and by such field measurements of the thickness of the shales in workable beds and such rude field distillation tests as will afford primary information concerning the amount and richness of the shales in different parts of the region. Very rough but cautious calculations of the contents of the shale in parts of the area examined indicate that the distillation of shale from beds over 3 feet thick in Colorado alone will yield more than 20,000,000,000 barrels of crude oil, from which more than 2,000,000,000 barrels of gasoline can be extracted by ordinary methods. A report giving the results of these explorations and tests and an account of experiments as to possible gasoline production, both by the ordinary commercial processes and by the Rittman process, is now in press.

THE SEARCH FOR POTASH.

The search for potash has continued with unabated zeal. The project of drilling in Smoke Creek Desert, Nev., outlined in last year's annual report, was completed, four deep wells having been put down at selected points in that locality. No potash of commercial importance was found. However, the fact has from the first been clearly recognized that the chances of success in this search must necessarily be small at most places, for the area in the western 62656°-INT 1916-VOL 1-21

United States to be explored is large and the funds available for tests by deep drilling must limit these tests to a few places each year. The surface indications that may help in determining places for drilling are only of the most general nature, yet these have been utilized with skill and judgment in the location of the tests made, and it is not questioned that the possibilities fully justified those tests.

In view of the character of the deposits encountered in the tests of the Quaternary lake beds of the Great Basin region it was concluded that probably there were better prospects of discovering deposits of potash and other salts in the Permo-Triassic "Red Beds" of the Southwest and of the Rocky Mountain region. The field examinations of the "Red Beds," to which reference was made in the last report, clearly indicated the occurrence of several periods of dry climate while this series of beds was being laid down, with consequent evaporation of continental water bodies, and these field studies have also disclosed interesting evidence of the deposition by evaporation of enormous deposits of rock salt, gypsum, and anhydrite in parts of the "Red Beds" country, especially in eastern New Mexico, northwestern Texas, and western Oklahoma.

Most of the drilling for water or for oil in this region has been confined to a few localities, so that in large areas the drill has never penetrated the deeper strata and the interbedded saline deposits. However, the drilling already done shows the presence of as much as 600 or 700 feet of buried rock salt in parts of the great "Red Beds" region. Potash, if present in stratified precipitate, should be associated with some of these saline deposits. Furthermore, the strata of this region, which consist largely of red sandstones and shales, thin dolomites, and gypsum, are similar in composition and general character to those that contain the great potash deposits of Germany, where also large deposits of gypsum and rock salt lie between the rock beds. It should also be noted that the periods of aridity and of saline deposition in the southwestern part of this country were essentially contemporaneous with the periods of evaporation and precipitation in the Stassfurt district. Finally, crystals of potash salts were found in the waste from a bore hole near Boden, not far from Amarillo, Tex., by Dr. J. A. Udden, of the Bureau of Economic. Geology and Technology of the University of Texas, and he also found traces of potash in muds or brines from several other wells, the earliest discovery-that in the brines of the well at Spurr, in Dickens County-having been made by Dr. Udden while he was examining drill samples and studying drill logs from western Texas under the auspices of the Federal Survey.

The facts cited justify the hope that beds of potash salts, possibly of commercial importance, may lie buried somewhere in the great "Red Beds" region of the Southwest. Such deposits were perhaps

precipitated only in very small areas in much reduced remnants of the shallow seas of the period. If they exist, they are likely to be lenticular, and, though their areal extent is problematic, they are doubtless of very slight extent in comparison with the great area of the "Red Beds." It therefore follows that if lenses of commercial importance exist in these beds a large number of holes may be drilled in different areas, even under the best geologic guidance, before such a lens is penetrated by the drill. On the other hand, it is possible that drillers may already have penetrated such lenses in their search for oil or water without recognizing the fact, for generally no analyses of the "brines" or the "salt beds" so encountered are made by owners or drillers. At the present rate of the Geological Survey's drilling tests in this region, it must be expected that many years may pass before the drill shall penetrate a single lens. Nevertheless, the need of getting adequate supplies of cheap potash in this country— and none are likely to be so cheap or so adequate as those that lie buried in the earth-is obviously so great and so imperative as to leave little doubt of the wisdom or, possibly, the necessity of incurring the expense of discovering them or proving that they do not exist.

There are indications that a great basin of salt water was evaporated in the Panhandle region of northern Texas, and as potashbearing crystals of salt were found near Boden, and traces of potash are said to have been found in brines or muds from wells at two or three other localities in this general region, a place at Cliffside, 7 miles northwest of Amarillo, was chosen for the first test to be made by the Survey in the "Red Beds" country. Accordingly, after the tests in the Smoke Creek Desert, Nev., were completed, the drill was shipped to Cliffside, where the owners of certain lands generously permitted the Survey to use them for like tests under terms of option by the Government. Work was begun in the autumn, and, in spite of such accidents as are usually incidental to boring in the "Red Beds," the hole was carried to a depth of 361 feet before the balance of the funds available for potash exploration was exhausted.

It is hoped that with the funds provided in the appropriation for the fiscal year 1917 it will be possible to continue this well to a depth of at least 1,800 feet, which should be sufficient to determine the stratigraphic position and the character of the deposits that furnish the red potash-salt crystals near Boden, if not to carry it to the base of the lowest salt bed, which is probably at a depth of nearly 2,300 feet. This drill hole, which should afford a thorough test of the questions raised by the indications found near Boden, will, however, be conclusive only for this area and, if unsuccessful,

can not be regarded as condemning other areas in the "Red Beds" region.

Meanwhile, efforts are being made to enlist the cooperation of drillers for oil and water at all points in the "Red Beds" country at which beds of rock salt are known or suspected to lie buried, in order that samples of brines and salt and of the rocks adjacent to the salt beds may be sent to the Survey for rough tests as to their possible content of potash salts in commercial amounts. In passing, it may be noted that the studies in this region point to the presence in western Texas, eastern New Mexico, western Oklahoma, and southern Kansas of one of the greatest rock-salt reserves of this continnent, if not of the world.

In this year, as in previous years, field examinations were made of all reported deposits of potash salts or nitrates that the samples or other information showed were worthy of field investigation and tests. The alunite deposits near Marysvale, Utah, were reexamined, and a report was published giving rough quantitative estimates of the quantity of potash they contain. Further, to supply a growing demand by chemical engineers for information as to the possibility of extracting potash and other products from various potash silicate rocks, field examinations, with adequate sampling for chemical analysis in the Survey laboratory, have been made of the greensands of New Jersey, Delaware, Maryland, and western Tennessee and of the sericite deposits in North Carolina and Georgia. During the year a paper calling attention to the potash content of tailings of certain copper and gold ores was published.

THE MINING-DÉBRIS PROBLEM.

A notable contribution to geologic literature in its broadest relations has during this year been completed for publication. The report, which will be issued during the coming year, is entitled "Hydraulic mining débris in the Sierra Nevada" and represents an extremely thorough investigation by Grove Karl Gilbert. To illustrate the scope of the investigation and of the report now completed, the circumstances under which this work was begun should be mentioned. In a memorial presented to the President of the United States in 1905, the California Miners' Association, after emphasizing the contribution of placer and hydraulic mining to California and to the Nation, expressed the conviction that a rational application of the natural laws governing the deposition of sediment from torrential streams would permit both hydraulic mining and agriculture to be carried on in this region, not only without prejudice to each other, but to their mutual advantage. In the belief that the question was primarily geologic, as it involves the study of erosion and of sedimentation in the mining districts as well as in the lower

valley regions, the association requested that the Director of the United States Geological Survey should be instructed "to undertake a particular study of those portions of the Sacramento and San Joaquin valleys affected by the detritus from torrential streams."

The investigation then begun by Mr. Gilbert was planned to include a field study of the natural phenomena connected with the problem and a laboratory study of the laws of transportation of detritus by running water. The results of this laboratory study have already been published in the Survey's Professional Paper 86— "The transportation of débris by running water"—and the report just prepared, which deals with the geologic and physiographic phases of the problem. presents the results of the completed investigation and contains conclusions much broader than the answers to the specific questions raised by the California Miners' Association.

This report, which will be published as Professional Paper 105, will rank as one of the largest contributions of the United States Geological Survey to geologic and engineering science and will also assist materially in solving this problem, which involves mining, agriculture, and navigation. To make such an investigation eminently successful, it has been necessary that the investigator should unite an aptitude for close observation and for logical interpretation with a habit of determining quantitatively as many as possible of the factors of the problem in hand. To his task Mr. Gilbert has brought these qualities in a marked degree, with the result that his report is a masterpiece wherein geology and engineering both contribute to the solution of a practical problem of the first rank. Especially important has it been that this subject should be viewed with the broad outlook of the geologist who appreciates the time factor that enters to so large a degree into any reaction of crustal change, erosion, and sedimentation. The studies cover every phase of the subject, from the original source of the detritus in the Sierra Nevada to the possibility of its transportation through the Golden Gate to the Golden Gate Bar, and in his broad treatment Mr. Gilbert has not only estimated the waste due to agriculture, grazing, roads and trails, and mining and studied its movement seaward, but he has supplemented his observations and estimates with instrumental surveys of impounded detritus as well as with measurements of tidal currents in the Golden Gate. This investigation utilizes the results of the earlier work by the Army engineers and has also had the benefit of generous cooperation by the officials of the United States Coast and Geodetic Survey, the United States Weather Bureau, the Lighthouse Service, and the United States Board of Engineers for Rivers and Harbors.

The investigator appreciated the fact that the problem intrusted to him was complex, involving many factors other than those directly