Sections of coal bed sampled in Robinson and Smith mines.

After the sample was cut, collected on a waterproof cloth, and broken small enough to pass through a half-inch mesh screen it was quartered down to about 4 pounds, sealed in an air-tight can, and mailed to the Bureau of Mines at Pittsburgh, Pa., where the analysis was made by standard methods. The analysis of each sample is given in four forms, marked A, B, C, and D. Analysis A represents the condition of the coal at the point in the mine from which the sample was cut. Analysis B shows the condition of the sample after drying at a temperature slightly above the normal until its weight remains constant. Analysis C gives the theoretical condition of the coal after all the moisture has been expelled. Analysis D represents the coal free from both moisture and ash. This is supposed to represent the true coal substance free from the principal impurities. Forms C and D are obtained from the others by recalculation. They should not be used for ordinary comparison, as they represent theoretical conditions that never exist.

In analytical work it is not possible to determine the proximate constituents of coal with the same degree of accuracy as the ultimate constituents. Therefore the air-drying loss, moisture, volatile matter, fixed carbon, and ash are given to one decimal place only, whereas the ash (in an ultimate analysis), sulphur, hydrogen, carbon, nitrogen, and oxygen are given to two decimal places. It should also be understood that the calorific determination to individual units is not reliable; therefore, in the column headed "Calories" the heat values are given to the nearest five units and in the column headed "British thermal units" they are given to the nearest tens (the value of the British thermal unit being about one-half that of the calorie).

Coal analyses.

a Volatile matter determined by the modified official method.

19799. Subbituminous coal from drift mine of Heber Robinson, in sec. 28, T. 5 N., R. 5 E., in Toone Canyon, 12 miles northeast of Devils Slide station on Union Pacific Railroad. Roof is shale and floor is coal. Sample probably slightly weathered; cut 300 feet northeast of opening September 5, 1914, by F. R. Clark.

19800. Subbituminous coal from abandoned slope mine of W. Lucas and H. C. Smith, in sec. 17, T. 5 N., R. 5 E., on west side of Lost Creek, 12 miles northeast of Devils Slide station on Union Pacific Railroad. Roof is shale and sandstone and floor is shale. Sample slightly weathered; cut from rib 200 feet west of opening September 5, 1914, by F. R. Clark.

COMPARISON OF SUBBITUMINOUS COALS OF THE REGION.

The above table of analyses includes samples of subbituminous coal from the Lost Creek field and from rocks presumably of the same age in near-by fields in Utah and Wyoming. The analyses indicate in a general way the chemical character of the coal in each field. That from Coalville, Utah, and Almy, Wyo., appears to be the best because the coal contains less moisture and ash and shows a greater heating value.

The moisture in the Lost Creek coal is considerably higher than in the Coalville and Almy coals; the ash is from three to four times greater and the heating value is considerably less than in the other coals; and the sulphur in the Lost Creek coal is less than in the Coalville coal but greater than in the coal from Almy, which is exceptionally free from sulphur.

The chemical constituents of a coal which most vitally affect its commercial value are moisture, ash, and sulphur, but the heating value is the all-important factor.

The rapidity with which a coal disintegrates and is reduced to slack depends largely on the percentage of moisture it contains. Therefore, a coal with a low percentage of moisture possesses stocking qualities superior to one with a high percentage. The Lost Creek coal, containing a high percentage of moisture, is not a good stocking coal and would soon disintegrate on exposure to the air. A high percentage of moisture is also objectionable, because the moisture replaces its weight of combustible matter, and a part of the heat generated by combustion is used in evaporating the moisture.

The percentage of ash in coal also materially affects its commercial value. The ash not only displaces its own weight of combustible matter, but during combustion a part of the heat generated is used in heating the ash. The high percentage of ash increases the cost of shipping and also of handling the coal in a power plant and decreases the efficiency of the furnace.

The ratio of the volatile matter to the fixed carbon indicates in a general way the type of furnace best adapted for burning a coal with maximum efficiency. A low-volatile coal may be burned in a

common type of furnace without throwing off much smoke (unburned carbon), but the smokeless burning of a coal high in volatile matter requires a specially constructed furnace.

A high percentage of sulphur is objectionable in coal used for the manufacture of coke and gas or for the generation of steam.

The relatively low heating value of the Lost Creek coal compared with the coals from Coalville and Almy is due chiefly to the fact that the impurities in the Lost Creek coal are three to four times as great as in the other coals.

FUTURE DEVELOPMENT.

Wyoming, Colorado, and Utah contain great quantities of bituminous coal which is likely to be the first to be developed on a large scale, and therefore even the best subbituminous coal in these States will not be developed except to supply local demands. The Lost Creek coal, being inferior in rank to subbituminous coal of near-by fields, is not likely to receive serious attention. Moreover, the coal in the Lost Creek field occurs in areas so small that probably it can not be developed as a shipping coal. Apparently its production in the future, as in the past, will depend upon local consumption.

STRUCTURE AND OIL RESOURCES OF THE SIMI VALLEY,

SOUTHERN CALIFORNIA.

By WILLIAM S. W. KEW.

INTRODUCTION.

Within the last few years considerable activity has been manifested in the development of a small oil field about 2 miles north of Santa Susana, Cal., a small town on the Coast Line of the Southern Pacific Co., about 32 miles northwest of Los Angeles, in the Simi Valley, Ventura County. (See index map, fig. 45.) The first wells in this region were put down by the Simi Oil Co. in 1900 near an oil seepage 14 miles east of the present producing fields. They obtained some oil of rather high gravity (32° Baumé) but not enough to make it a paying investment. In 1912, after a geologic report had been made, drilling was begun by the Petrol Oil Co. on the axis of an anticline in Tapo Canyon, where a well was brought in which yielded a fair production of light oil (35°-36° Baumé). Since then a number of wells have been drilled with success.

1

Although this region has been visited frequently by geologists, comparatively little information has been published concerning the geology either of the oil fields or of any other area on the south side of the Santa Susana Mountains. In the fall of 1917 a geologic survey covering the whole Simi district was made by the writer in order to determine as far as possible from surface indications, aided by drilling records, the future possibilities of the existing fields and to find any other localities where the structure is favorable for holding oil. This paper is preliminary to a complete report on the geology and oil resources of the Santa Clara Valley, Santa Susana Mountains, and Simi oil districts, which is now in preparation. During this work the writer was assisted by Carroll M. Wagner, whose notes have aided materially in making this report. Opportunity is taken to express the writer's appreciation for the uniform kindness and much valuable information given by the operating oil companies and by the residents of this district.

Johnson, H. R., Geologic notes on Santa Susana district: Western Eng., vol. 2, No. 5, pp. 383-386, 1913. Waring, C. A., Structural geology south of the Santa Susana district: Western Eng., vol. 3, p. 470, 1913. Waring, C. A., Stratigraphic and faunal relations of the Martinez to the Chico and Tejon of southern California: California Acad. Sci. Proc., vol. 7, No. 4, pp. 41-124, pls. 7-16, 1917.