ments of water-loss by evaporation. The reading may be nil or even negative (entrance of water into the reservoir), in spite of the actual evaporation of significant amounts of water from the instrument during the periods between showers. It is not feasible to correct for these errors of water absorption, but the difficulty has long been practically overcome by the employment of a rain-correcting, or non-absorbing, mounting for this kind of atmometer when operated in the open during rainy weather. All the non-absorbing mountings thus far suggested depend upon a mercury valve that allows water to pass through the tube freely in the upward direction, but practically prevents movement downward. As soon as liquid water is deposited on the exposed porous surface the surface automatically becomes virtually impervious to water from without, and the precipitation water runs off from the instrument as though it were glazed. When the rain ceases the valve reverses and evaporation soon begins to be registered as water-loss from the reservoir. Various types of mercury-valve mounting have been described, but the Shive form has been most generally used. All these nonabsorbing mountings are relatively expensive, and the least expensive one (Johnston's) involves the use of rubber and requires special care in the installing of the instrument. A much simpler form of mounting than any hitherto sugested has recently been tested in the Laboratory of Plant Physiology of the Johns Hopkins University. The purpose of this paper is to place the new modification in the hands of those who are interested in atmometry, so as to save them the expense and troubles of the more complicated mountings. 2 Livingston, B. E., "A Rain-correcting Atmometer for Ecological Instrumentation,'' Plant World, 13: 79-82, 1910. Harvey, E. M., "The Action of the Rain-correcting Atmometer," Plant World, 16: 89-93, 1913. Shive, J. W., "An Improved Non-absorbing Porous-cup Atmometer, Plant World, 18: 7-10, 1915. Johnston, E. S., Simple Non-absorbing Atmometer Mounting," Plant World, 21: 257-260, 1918. "A The new mounting is very simple. The porous-porcelain piece is mounted in the usual way, by means of a rubber stopper, on the upper end of a glass tube of suitable length and having a bore of about 6 or 7 mm. This tube bears a second rubber (or cork) stopper somewhat below the first, which fits the mouth of the reservoir bottle and closes it completely as far as entrance of rainwater is concerned. The reservoir stopper is not slotted to allow air entrance to the reservoir, but access of air to the interior is allowed through a short, inverted-U-shaped glass tube, one arm of which is longer and penetrates just through the reservoir stopper from without, while the other arm is shorter, is directed downward and terminates a few millimeters above the upper surface of the stopper. This U-tube may be very small and its end may be loosely plugged with glass wool to exclude insects, etc. A water-proof apron over the top of the reservoir may be employed (Livingston, 1908), or other devices to allow air entrance and to exclude rain water may be used. Thus far we have an absorbing mounting, suitable only for indoor operation or for periods without precipitation. But a very simple and efficient mercury valve is inserted in the upper end of the straight tube, as follows. A tightly rolled plug of glass wool (about 1 cm. long) is inserted in the upper end of the tube, the outer end of the plug is cut off so as to have a flat surface, and it is pushed into the tube until its upper end is about 2 cm. from the top of the tube. Next, a small amount of mercury is placed in the tube above the plug (the mercury column being 5-8 mm. high) and another plug of like nature is inserted above the mercury. The mercury is imprisoned between the two plugs and can not escape, in whatever position the tube is placed. To install the instrument, the tube is inverted and the end bearing the valve is inserted in distilled water while suction is applied at the other end. Water enters freely through the valve and the tube is nearly filled in this way. Then the porous-porcelain piece (cylinder, sphere or Bellani plate) is filled with distilled water and the tube is set into the porcelain piece, with the rubber stopper pressed firmly into the neck. The tube is next completely filled with distilled water, by pouring from the reservoir bottle (previously filled), and then it and the porcelain piece together are quickly inverted and the free end of the tube is inserted into the reservoir in the usual manner, the second stopper closing the reservoir. With the arrangement here described water does not pass downward through the valve, but it readily passes upward, keeping the evaporating surface supplied. This mounting appears to operate perfectly, just as well as do the more complicated forms, it is more easily installed than they, it is easily constructed and the materials are inexpensive and readily obtainable. BURTON E. LIVINGSTON, THE JOHNS HOPKINS UNIVERSITY Vernon; First Vice-president, D. W. Morehouse, Drake University, Des Moines; Second Vice-president, R. B. Wylie, State University, Iowa City; Secretary, James H. Lees, Iowa Geological Survey, Des Moines; Treasurer, A. O. Thomas, State University, Iowa City. The academy ratified the action of its executive committee in accepting affiliation with the American Association for the Advancement of Science, which action had been taken soon after the meeting of the association in St. Louis. The constitution was amended to provide for the collection of dues of the association by the treasurer of the academy at the same time as the academy dues, and also to provide for the beginning of the fiscal year on October 1. Also an amendment was passed providing for the selection by the academy of a representative on the council of the American Association for the Advancement of Science. The Iowa sections of the American Chemical Society and the Mathematical Association of America held their meetings in conjunction with the academy. THE IOWA ACADEMY OF SCIENCE THE thirty-fourth annual session of the Iowa Academy of Science was held in Physics Hall of the State University at Iowa City on April 23 and 24. At the opening session on Friday afternoon, the twenty-third, the memorial portrait of the late Dr. Samuel Calvin, formerly head of the department of geology at the state university and state geologist, was unveiled and presented by the Academy to the State Historical Department at Des Moines. President Stephens then delivered his address on "The Taxonomic Unit.'' After the reading of papers the academy adjourned to see the moving pictures showing the University Barbados-Antigua Expedition of 1918 and also those showing the development of the potato disease known as "Leak" by the fungus Pythium DeBaryanum. Owing to the fulness of the program it was necessary to hold a short sesion after the group dinners, following which President Jessup, of the university, and Mrs. Jessup received the visiting members at their home. Section meetings were held on Saturday forenoon and at the succeeding business session the following officers were chosen for the coming year: President, Nicholas Knight, Cornell College, Mount TITLES OF PAPERS Botany The treatment of certain seed-carried diseases: GUY WEST WILSON. This paper deals with work on cotton diseases conducted by the author and associates at the South Carolina Experiment Station. Cotton anthracnose is the most important disease of field crops in the southeastern states, comparing favorably with the wheat rust in the Mississippi valley. The author and his associates have perfected a method of treating the seed which is practicable on a commercial scale and which bids fair to be of considerable value in the treatment of seed carried diseases of other crops. Some noteworthy uredinales and ustilaginales: GUY WEST WILSON. Notes on apogamous Liguliflora: RAYMOND A. FRENCH. Some aspects of the plant ecology of certain Kansas sand hills: FRED W. EMERSON. The sand hills studied lie in south-central Kansas along Arkansas river between Wichita and Hutchinson. Dense vegetation holds the sand stable wherever man permits; burning, close grazing and attempts to plant farm crops have removed natural vegetation from considerable areas not only making them useless but threatening neighboring farm lands with being covered with blowing sand. All degrees of reclamation by invading vegetation are found. The types and characteristics of the plants are noted and short lists of the more important plants found at the various stages are given. Notes on some Rocky Mountain plants, chiefly of the Arapahoe mountains: L. H. PAMMEL AND R. I. CRATTY. Further notes on the germination of some trees and shrubs and their juvenile forms: L. H. PAMMEL AND CHARLOTTE M. KING. On the occurrence of the giant puff ball: HARRY M. KELLY. The disintegration of certain intracellular bodies: The teaching of plant pathology: W. H. DAVIS. The vegetation of Cape Blanco: MORTON E. PECK. Some Alaska fungi: J. P. ANDERSON. The genus Ceanothus in Iowa: B. SHIMEK, Notes on the distribution of midsummer bee plants in the Mississippi zone of Clayton county: ADA HAYDEN. The growth of foliage leaves: BERYL TAYLOR. Comparison of the absorption occurring in corn stalk tissue and in prepared bicolloids: L. E. YOCUM AND A. L. BAKKE. Mechanical preparation of sweet corn pericarp: R. A. RUDNICK AND A. L. BAKKE. The Orchidacea of Nebraska: T. J. FITZPATRICK. The influence of forest areas in non-forest regions upon evaporation, soil moisture and movement of ground water: I. BODE. The paper includes the results of a series of studies carried on in the northeastern part of Iowa during the summer of 1919. The work covers a comparison of the evaporation and soil moisture conditions obtaining on forested and non-forested sites, and the influence that forested areas have as to the checking of runoff, the absorption of moisture in the soil and the response of various soils at various depths to precipitation. The results and conclusions bring out some very interesting facts relative to the economic values of forest areas of a state like Iowa in conserving soil mois ture, checking evaporation and regulating the flow of smaller streams throughout the state. Chemistry Simplified electrotitration and its use in determin- An apparatus for determining solubilities up to Vacuum tube circuits as a source of power for conductivity measurements: H. A. GEAUQUE. The free energy of dilution and the activity of the ions of sodium bromide: J. N. PEARRE AND H. B. HART Geology Iowa terranes compared with those of adjoining states: CHARLES KEYES. Since geologic phenomena are not restricted by political boundaries many of the missing leaves of Iowa's earth-history are found clearly imprinted in contiguous states. But it is difficult to make very close comparisons because of the diverse conditions and the varied aims under which the terranal schemes are constructed. By reducing to a standard the geological sections of our state and those of surrounding states a classificatory plan is effected which, although perfectly elastic, permits exact stratigraphic parallelism to be instituted. Belated survival of Wernerian nomenclature: CHARLES KEYES. Galena as denominating a notable Ordovicic dolomite is not a geographic name, as is so often supposed. James Hall, who proposed the term, derived it directly from the chief mineral content of the formation. In using the title this author manifestly modified Featherstonough's earlier name "Galeniferous Limestone," which in turn was an alteration of Schoolcraft's usage of "Metalliferous Limestone."' Rectification of Iowa's Cambric section: CHARLES KEYES. Recent critical inspection of the type localities of the Cambric formations of the upper Mississippi basin indicates that there are grave misinterpretations of stratigraphic succession. Thus, some well-known formational titles become synonyms and pass out of use; several names are new; and a number of substitutions appear. Exact parallelism of the upper Mississippi Basin section and that of the Ozarks is thus satisfactorily permitted. The use of the terms flint and chert: W. S. GLOCK. Common usage of these terms may leave such an uncertainty that a word dare not be employed where scientific accuracy is desired. For example, It is a common habit to call any form of quartz interbedded with iron ore "chert" for want of knowledge of the nature of the quartz and of the meaning of the term employed. Detailed reference to the standard English and American textbooks on geology and mineralogy substantiates the confusion which exists and which is presented therein for the instruction of the reader. Neither chert nor flint should be a provoking "'catch-all''; fundamentally they are good terms whose use is justified only where exactness is implied. The fauna of the Independence Shale: A. O. THOMAS. This interesting fauna, first reported by Dr. Calvin over forty years ago from a very limited exposure, has recently become better known due to the discovery of several fossiliferous outcrops of the shale as reported before the academy a year ago. Among the additions to the fauna is a species of the crinoid Arthracantha, hitherto known only from the Devonian of the region of Lake Ontario. There is also a species of Spirifer akin to 8. disjunctus, a new Chonetes, and a fine specimen of Hypothyridina cuboides. A few of the species of the Independence shale recur in the Lime Creek hale at the top of the Iowa Devonian but none of the forms just mentioned are known to occur in the later formation. Nortonechinus, a Devonian sea urchin: A. O. THOMAS. This is a highly specialized genus known only from dissociated plates, spines, and parts of the lantern. The test of the living animal was doubtless very flexible and was well protected by the covering afforded by the broadly expanded distal ends of the spines as in modern Colobocentrotus. Two other genera of echinoids also found in the Lime Creek shales will be briefly discussed. The corals of the Hopkinton stage, Iowa Silurian: A. O. THOMAS AND BERYL TAYLOR. The Iowa Silurian affords a rich and interesting assemblage of corals most of which are highly silicified. The Calvin Collections from the typical localities together with those made by various field classes and by the writers, furnish a large series in which some of the genera are very well represented. Strombodes, for example, has no less than ten species, Favosites, seven, Zaphrentis, six, and Heliolites, four. The reefs furnish upwards of seventy species, many of which are new. The conservation of underground water: JAMES H. LEES. its The paper discusses the importance of water, source and distribution, its relation to the rock strata and its use by plants. The need for better conservation is emphasized and the effect of population increase and of agriculture is discussed. Certain post-Pliocene deposits in Missouri: B. SHIMEK. On the occurrence of charcoal in an interglacial peat bed in Union county: RALPH W. CHANEY. A sink hole in northeast Iowa: E. J. CABLE. A field of eskers in Iowa: JOHN E. SMITH. The Palisades of the Cedar: WM. H. NORTON. Physics The Hall effect and the specific resistance of thin silver films: G. R. WAIT. The dependence of the resistance of silver films LETT. The perception of binaural phase difference not caused by an intensity effect: G. W. STEWART. The frequency limits of the binaural phase difference and intensity effects: G. W. STEWART. Note on the principle of similitude: I. MAIZLISH. A table of the total number of stroboscopic veloc ity curves for any of the natural numbers from 1 to 500 inclusive taken as a limiting value of n and m: L. E. DODD. On finding the equation of the characteristic blackening curve of a photographic plate: P. S. HEL MICK. The overtones of air columns: L. B. SPINNEY. The stereoscope in teaching physics and geometry: LEROY D. WELD. The stereoscope has usually been considered a mere toy. In this paper, however, is given a method whereby stereoscopic drawings of any simple figure in space can be easily prepared and duplicated for use in the study of any subject requiring three-dimensional figures, such as solid geometry, crystal structure, analytic mechanics, optics, etc. Psychology Symposium: Some Results of Current Research in the Psychological Laboratory of the State University. Introduced by C. E. Seashore. The talent survey in our music school: ESTHER ALLEN GAW. The Iowa pitch range audiometer: C. C. BUNCH. The normal curve of acuity in hearing: PAUL B. ANDERSON. The localization of sound by wave phase in the open ear: HENRY M. HALVERSON. What constitutes voice: CARL I. ERICKSON. The application of the Mendelian law to talent in music: HAZEL M. STANTON. The personal equation in motor capacities: MARTIN L. REYMERT. Serial action as a basic measure of motor capaci ties: C. F. HANSEN. The measurement of motility in children: LILLIAN Tow. The selection of talent for stenography and typing: B. W. ROBINSON. A measure of capacity for acquiring skill in coordination of eye and hand: WILHELMINE KOERTH. A standardized measure of motility: MERRILL J. REAM. Zoology Some Iowa records of Lepidoptera: A. W. LINDSEY. A biological reconnaisance of Okefinokee swamp, Georgia. The fishes: E. L. PALMER AND A. H. WRIGHT. The Okefinokee swamp in its fish fauna is decidedly fluviatile. Like that of Florida its fish fauna may be held to have "originated from the north and is thus not tropical." The swamp has twenty-three less fresh water species than the whole state of Florida and in number of forms is not comparable to the better known Everglades of Florida. Twenty-eight species are known from the swamp and twenty-two of these are included in the collection upon which this paper is based. Sixty three specimens of the rare Lucania ommata (Jordan) were taken. The southern limit of the range of Umbra limi (Kirtland) is increased from North Carolina to southern Georgia. In addition the material supports contentions that Umbra pygmæa DeKay is a synonym of Umbra limi (Kirtland); Esox vermiculatus Le Sueur, of Esor americanus (Gmelin.); Enneacanthus gloriosus (Holbrook), of Enneacanthus obesus Baird; and Copelandellus quiescens (Jordan), of Boleichthys fusiformis Girard. Bird records of the season 1919-1920 in the vicinity of Iowa City: DAYTON STONER. Cladocera of the Okoboji and Spirit Lake regions: FRANK A. STROMSTEN. Copepoda of the Okoboji region: FRANK A. STROMSTEN. Rotatoria of the Okoboji region: DWIGHT C. ENSIGN. Similarities between the lateral-line systems of elasmobranchs and amphibians: H. W. NORRIS. Naked neuromasts in amphibians correspond to pit-organs and canal-organs in the elasmobranch fishes. The mandibular series of neuromasts of amphibians is distinctly double, oral, and gular. Similarly in elasmobranchs the mandibular and hyomandibular canal organs correspond to the oral series and a mandibular row of pit-organs to the gular series of neuromasts of amphibians. The vaguely defined occipital group of neuromasts of amphibians corresponds to the sense-organ of the supratemporal canal. Three lines of neuromasts occur on the trunk of the body in amphibians, innervated by three distinct nerve rami. Three series of lateral-line organs are to be found on the trunk in elasmobranchs. Susceptible and resistant phases of the dividing sea-urchin egg when subjected to various concentrations of lipoid-soluble substances, especially the higher alcohols: FRANCIS MARSH BALDWIN. When subjected to suitable concentrations of various lipoid-soluble substances the developing seaurchin egg shows unmistakable rhythms of sus |