black blotch indicates an extensive oil pool in McCurtain County in the southeastern corner of Oklahoma where actually the only indication of oil thus far found is some asphalt. In contrast to the addition of this non-existent field a number of small fields are omitted. As the map is drawn to a small scale, this is quite excusable in many instances where the fields would appear as insignificant dots near the much more conspicuous blotches that represent large producing areas. However, such significant developments as the small field east of Cushing and north. of Bristow, the little Barnes field between Billings and Garber, the small pool at Holdenville in Hughes County, and the field at Cement in Caddo County, Oklahoma, and the Avis field in northeastern Jack County, Texas, should be shown.

Like the omission and inaccuracies on the map many of the errata are doubtless due to carelessness. Thus, on page 8, the author mentions the oil fields of Missouri separated from the Mid-Continent field by the Ozark uplift, when he probably has in mind the fields of western Illinois. The statement on page 16 that late in 1915 the Healdton field was yielding 90,000 barrels a day could be nothing but an error in copying, for this figure has not been given in any statistical report of the field's output. Errors of this type are harmless to the man who is fairly well versed in the petroleum geology and history of development in the MidContinent region, but become serious when they are seen and accepted by uniformed readers.

The contradictions are not so serious, although they detract greatly from the value of the book. In some instances the principle of majority rule can be applied. For example on page 147 Healdton oil is said to range in gravity from 42.7 to 27° Baume. At the same place the gravity is given as .8105 to .8383, which would make the range from 42.7 to 37° Baume. On page 209 the gravity of Healdton oil is given as 29.37 to 33.93 Baume. By turning to page 31 where there is a tabulation of the oils from different fields, confirmation of the last figure is obtained. Similarly on page 220 the author says the Strawn field is on a small "nose" but on both page 137 and page 223 the statement is made that it is on a small dome. On page 132 the deep oil of the Electra and Burkburnett region is credited to the Cisco formation, but on pages 134, 135, and 139 it is ascribed to the Canyon formation.

Still more serious are repeated misstatements concerning stratigraphy, structure, and production. One of the most glaring of these is the consistent reference to the Bend formation of Texas as Mississippian, in contradiction to the findings of Girty, Moore, Udden, Plummer, and Roundy, who have made careful determinations of the fauna, showing that unauthoritative statements in trade journals have been accepted

without attempt at confirmation from those who may be regarded as authorities. The statement on page 132 that there are Permian strata in the western part of Okmulgee County is refuted by the geological boundaries shown on the frontispiece. Similarly, if, as the author states, the deep production of the Yale field comes from the Mississippian, the map on page 53 showing the attitude of the Mississippian in Oklahoma must be in error. The assertion on page 141 that the red Permian beds are productive only in southern Oklahoma and northern Texas disregards the Garber field where the Hoy sand, high above the base of the Permian, has given notable production.

A serious shortcoming of the book is the paucity of references. A meager bibliography of 42 references and an occasional mention of the source of information does not furnish the aid to investigation that a work of this type should. The lack of confidence that results from the author's errors in statement makes this absence of adequate references particularly lamentable. Such references as are given are frequently incomplete.

The illustrations are also a point of weakness. Many points that could be made clearer by simple figures or diagrams have been left unillustrated. Some of the illustrations have been adapted from other publications without taking into consideration the effect of a necessary reduction in scale. The result has been to make the figures and words on some of these illustrations so small that they approach illegibility.

The arrangement of the book makes it unsatisfactory as a reference work. To obtain the data relating to any one field it is necessary to consult two, three, or four distinct sections of the book. Two sections on structure are separated by discussions of geological history of the oil bearing deposits and of stratigraphy in the oil field. There is a good deal of repetition which in many instances saves the reader the necessity of turning to another section of the book and although there are cross references these are incomplete, as they do not give the page number but only the part, section, and chapter.

The faults mentioned prevent this book from having much value as a handbook for the field geologist or a textbook for the student. The volume, however, does present in concise form many of the fundamental facts relating to the oil production in the Mid-Continent region and is therefore useful to any one unacquainted with the region who wishes to get a general idea of its history and of conditions obtaining there.

K. C. HEALD.

Microscopic Examination of Ore Minerals. By W. MYRON DAVY AND C. MASON FARNHAM. 154 pages, New York, McGraw-Hill Book Co. 1920.

As applied in this case microscopical examinations are confined to observations by vertically incident light on clean or chemically treated polished surfaces. The ore minerals considered are, with the exception. of about a score, too opaque to be studied advantageously by the more adequate methods in which transmitted light is used.

Definite directions are given for polishing, photographing and testing specimens. A determinative table of the minerals has been prepared on the basis of a few chemical reactions and of hardness tests on polished surfaces. Color and tenacity receive secondary consideration. The desirability of supplementing the microscopical examinations with certain physical tests and with blowpipe and other chemical tests is emphasized, and a chapter is devoted to such tests. "The microchemical reactions listed are from various sources. The authors have independently studied one hundred and forty-three mineral species . . .; and as most of these species are also listed in Dr. Murdock's book, it is believed that this triple check results in the accurate determination of the reactions."

One test depending primarily upon electrical conductivity is described so inadequately as to be of scarcely more than suggestive value. An erroneous conclusion might be drawn in Table 10 that covellite and magnetite have as great electrical conductivity as copper, whereas this table indicates only that one set of minerals (column 1) under the conditions named on pages 8 and 123 introduce resistances of less than about 2 ohms (that is, small in comparison with the resistance of the voltmeter); another set (column 3) introduce many thousand ohms; and a third set (column 2) introduce resistances of an intermediate range. The voltmeter readings of column 2 could not in general be reproduced under conditions which other observers could set up.

Sectile, a mineralogical term of rather definite meaning and application, is here used repeatedly in a different sense to describe certain effects produced by gouging a polished surface with a needle. By this test bornite and copper are "sectile" and chalcocite is very sectile." A new term is needed, and such expressions as "sectile, but slightly brittle," as applied to galena, should be defined.

For bornite the ill-chosen color term "pinkish brown" has survived. Turgite is not sufficiently characterized with respect to color, streak, and structure and the formula given is open to question. The cleavage of chalmersite should be mentioned. Wurtzite does not have the cleavage of sphalerite and neither gives a really yellow powder. The usual

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color of limonite by internal reflection is orange brown rather than reddish brown.

The formulas for calaverite, krennerite and sylvanite do not appear to correspond to the analyses; the following seem to be more nearly correct: calaverite and krennerite (Au, Ag) Te,, sylvanite AuAgTe.. H. E. MERWIN.

GEOPHYSICAL LABORATORY,
CARNEGIE INSTITUTE,
WASHINGTON, D. C.

SCIENTIFIC NOTES AND NEWS'

L. C. GRATON, geologist to the Calumet and Hecla Mining Co., is in Cambridge, Mass., temporarily. His present address is: Oxford Street, Cambridge, Mass.

FRANCIS B. LANEY, previously of the U. S. Geological Survey, has been appointed professor of geology in the University of Idaho School of Mines.

ALFRED H. BROOKS has recently returned to Washington from Alaska, where he has been investigating copper and oil deposits of the coastal region.

R. S. KNAPPEN has resigned from the faculty of the University of Chicago and is now teaching economic geology at the University of Kansas and devoting a part of his time to work in petroleum.

ALFRED W. STICKNEY, American mining geologist, has been captured by the Bolsheviki and imprisoned in Moscow.

HORACE V. WINCHELL recently returned from a professional trip to Alaska and has gone to Arizona.

E. S. MOORE, of the School of Mines, Pennsylvania State College, is pursuing the study of the refractories of Pennsylvania for the Pennsylvania Topographic and Geologic Survey Bureau and spent the past field season largely on the ganister deposits of the State.

R. M. OVERBECK, of the U. S. Geological Survey, returned from South America during the summer.

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1 Geologists, mining engineers and others interested in applied geology are invited to keep the editor informed of new investigations of mining districts or scientific studies undertaken by them, together with such other scientific and personal items as may come to their notice.