SECTION E, AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE X-RAY STUDIES OF SURFACE LAYERS OF CRYSTALS: A REVIEW OF THE FIELD WITH SPECIAL REFERENCE TO QUARTZ BY ELIZABETH J. ARMSTRONG The reflection of X-rays from crystalline material depends very precisely on the orientation of the crystal structure with respect to the X-ray beam: the intensity of the reflection is related to the structural perfection of the crystal. Based on these fundamental principles various techniques have been and are being devised for the X-ray study of structural disturbances in artificially prepared crystal surfaces and natural faces. These techniques are reviewed, and their potentialities and limitations are noted, with special reference to their use in the study of ground and lapped quartz surfaces. APPLICATION OF ELECTRICAL EARTH RESISTIVITY SURVEYS TO GROUND-WATER STUDIES IN OHIO BY RALPH J. BEKNHAGEN Earth-resistivity surveys operate on the fundamental premise that earth materials of different character react differently to the passage of an electric current. Average apparent resistivities are measured to various depths at different stations suitably located to accommodate the purpose of the investigation. The interpretation of the data obtained in such a survey may be used to determine: (1) the thickness of glacial drift overlying bedrock, (2) the depth and extent of a body of water and nature of the underlying material, (3) the locations of ore bodies and placer deposits, (4) the location of possible water-bearing sand and gravel deposits. Four electrodes are placed in a straight line in the ground at equal distances on a relatively plane surface; a commutated current is conducted into and through the ground between the two outer electrodes, and the voltage drop is measured between the two inner electrodes. The depth at which each reading is taken is determined empirically by the distance separating any two electrodes. The Ohio Water Supply Board has inaugurated in the past year a program of resistivity surveys to assist in the location of ground-water supplies for Ohio’s municipalities and industries, particularly in the glaciated area to delineate bodies of sand and gravel and to locate the channels of buried pre­ glacial valleys. The interpretation of the resistivity data is considered in the light of all known geological information for the area under consideration; the favorable water-bearing conditions are outlined, and the locations for test drilling are recommended. AN INTERPRETATION OF LOWER JAMES RIVER, VIRGINIA* BY ROBERT O. BLOOMER James River in Virginia, like other Appalachian rivers, has had a long complex geomorphic history. Certain peculiarities in the present course of the stream may be a key to its past history and may have some bearing on the interpretation of the regional geomorphology. Several changes in the average southeast course may be due to tilting, originating from an axis transverse to the southeast regional slope. These deviations from the southeast course may furthermore mark the location of former strands and thus indicate margins, at various times, of the Coastal Plain overlap. Also the course of James River is such that there seems to have never been an advanced stage of the geomorphic cycle such as maturity or old age. A channel, however, in the Coastal Plain overlap below Richmond may have been formed by James River during Lower Cretaceous time. Thus James River may have been a large stream as early as the Cretaceous but never reduced to or near base level. Consequently the Tertiary peneplain postulated by some geologists may be doubted. ‘Published with the permission of the State Geologist of Virginia. 1472 Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/55/12/1472/3426014/BUL55_12-1472.pdf by guest on 29 September 2021 SECTION E, ASSOCIATION FOR ADVANCEMENT OF SCIENCE 1473 AGING OF QUARTZ CRYSTAL OSCILLATOR PLATES BY VIRGIL E. BOTTOM Quartz plates of specific orientations are widely used to control the frequencies of radio oscil­ lators. The physical properties of quartz make it a nearly ideal material for this purpose. Serious difficulty has been encountered with high-frequency plates due to aging. This has been shown to be due to deterioration of the surface of the plate. The effect is associated with the action of water vapor on a layer of misaligned quartz which results from the operations of grinding, lapping, and polishing. The remedy is removal of the material by etching. When quartz oscillator plates are etched by an amount sufficient to remove the misaligned material, the surfaces are apparently stable, and aging is negligible. STAGES OF LAKE CHICAGO; THEIR CAUSES AND CORRELATIONS BY J HARLEN BRETZ The three stages of Glacial Lake Chicago record (1) the original lake level, (2) a time of rapid lowering because of outlet deepening, (3) a pause in this deepening and lowering, (4) renewed lower­ ing because of renewed outlet deepening, and (5) a final level determined by a bedrock sill in the outlet channel floor. The dam for the lake was not the Valparaiso moraine, as earlier students have thought, but the younger Tinley moraine and its outwash. The valleyway across the Valparaiso moraine is much older than Lake Chicago. No stopping by retreat of rapids, either in glacial drift or in bedrock, was involved in the times of outlet deepening or the pauses between those times. The outlet downcuttings are correlated with times when glacial lakes in the Erie and Huron basins discharged into Lake Chicago and greatly increased erosive action in its outlet channel. The two earlier static water levels record times when these eastern lakes discharged elsewhere and a boulder armor on the outlet floor brought deepening to an end. INTERLACING OF PIEZOELECTRICITY WITH OTHER BRANCHES OF SCIENCE BY W. G. CADY To what extent is our knowledge of piezoelectricity and our ability to put it to work dependent on an acquaintance with the various sciences? Conversely, to what extent has piezoelectricity contributed to the physical or other sciences? An attempt is made to answer these questions. The topics considered will include a brief account of the nature of piezoelectricity, its relation to crystal­ lography, and the methods for detecting or measuring the piezoelectric property; the use of thermo­ dynamic methods for expressing the relations between piezoelectric, elastic, and dielectric phenom­ ena; the interaction of these relations in the theory of the crystal resonator; the principles underlying the design of resonators, with regard to the various possible modes of vibration and their excitation and to the problem of making the vibrational frequency independent of temperature. Attention is directed to the use that has been made, in the progress toward this goal, of all branches of physics, but more particularly vibration theory, dielectric and electric circuit theory, polarized light, and X-rays; and in addition, geology, crystallography, and chemistry. COMPOSITION OF THE GLACIAL DRIFT IN OHIO BY G. W. CONREY Two features of importance in evaluating the composition of glacial drift are the content of carbonates and the amount of clay. Dilute muriatic acid has been widely used in testing for the presence of carbonate. Effervescence indicates the presence of carbonates but not the amounts. Texture of the material can readily be estimated from a determination of the consistence (plasticity, stickiness, etc.). These characteristics are of great importance in studies of the genesis of Ohio soils. Considering only the late Wisconsin drift, in western Ohio, where the underlying bedrock is chiefly limestone, the lime carbonate content varies from 25 to 45 per cent, the clay content from 15 to 24 per cent. In northeastern Ohio, where the bedrock is chiefly noncalcareous sandstone and shale, where the texture of the till is a loam, the drift may be noncalcareous to 6 or 8 feet below which there may be Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/55/12/1472/3426014/BUL55_12-1472.pdf by guest on 29 September 2021 1474 ABSTRACTS 2 to 5 per cent of lime carbonate border, where sandstones predominate. In contrast are the clay tills on the northern part of the belt where lime carbonate ranges from 1 to 18 per cent, and the day content from 28 to 49 per cent. The lime carbonate is confined largely to the fine material. A consideration of the direction of movement of the ice suggests, as the source of the lime carbonate, (1) the basin now occupied by Lake Erie, (2) the limestone deposits in Canada north of Lake Erie, (3) lime carbonate precipitated from percolating waters. Evidently it is necessary to recognize high-lime and low-lime drift. These weather to produce soils of markedly different characteristics. CORRELATION OF SOME COALS IN SOUTHERN WEST VIRGINIA BY USE OF PLANT MICROFOSSILS BY AUREAL T. CROSS Extensive investigations are being made of the plant microfossils contained in the Lower Allegheny and Kanawha coals of West Virginia. The stratigraphic and geographic ranges are being deter­ mined in an effort to establish proper index values for these microfossils. The most readily identi­ fiable plant residues, the megaspores, have been studied from about 35 coal horizons. Over 45 species, assigned to 14 genera, have been tentatively identified. These include more than 25 species of the large genus Triletes and several new species and varieties which await description. Investiga­ tion to date shows these spores to be fairly consistent geographically by their similar representation in the same horizons from each of several localities. These microfossils also furnish evidence of several major breaks in lithology of the strata involved. The most pronounced change in floristic composition occurs about the horizon of the Chilton “A” coal, which is between the Winifrede (Magoffin) and Salt Lick marine zones, or approximately in the position of the recently postulated boundary between the Allegheny and Kanawha series.