constant velocity of the spherical wave, and the other the decreasing velocity of the surface or emergent wave. By connecting these points by rectangular co-ordinates, an equilateral hyperbola is developed, the centre of which is the focus x, and the character of which depends on the depth of the focus. The hyperbola becomes more and more triangular in form as the depth becomes less (as in taking the surface at c'd', c"d"), until, if the focus is at the surface, the hyperbola becomes a right-angled triangle; i.e., the surface wave passes over equal spaces in equal times. If, therefore, we plot accurately the times on AB, and the corresponding places on CD, we may develop the hyperbola and calculate its centre; or else by accurate trial we may find a point which shall be the centre of circles passing through corresponding times and places. That point will be the focus. Such is a very general account of the method, given in my own way. For more accurate detail, Seebach's work must be consulted. We believe that this method, in a thickly settled country dotted over with observatories on railroad-stations where accurate time is kept, will prove the most accurate. Dutton and Hayden object to this method that it is important to have the accurate time of arrival of the wave, because there are two kinds of waves, - the normal and transverse, - which run with different velocities. The answer to this is, that it is only over a comparatively small area that, on any method, observation can be relied on for estimating depth. Inspection of Fig. 3 shows that the arm of the hyberbola very soon becomes almost straight; the velocity of emergence at any considerable distance becomes sensibly the same as that of the spherical wave, and therefore can no longer indicate depth. But over the small area where the curve of the hyperbola, or change of velocity, is rapid, the time of arrival of the different waves would not greatly differ. At any rate, the use of seismographs which decompose the complex earth-motions will record these different waves separately, and thus enable us to determine the law of decrease of one of them - the normal — with accuracy. In conclusion we would insist that we cannot any longer afford to study earthquakes without seismographs. The Geological Survey ought to have these in different parts of the country. The University of California has recently gotten three of these of the best character (Ewing's and Gray-Milne's), which will soon be set up in different parts of the State. JOSEPH LECONTE. Berkeley, Cal., June 21. The Corresponding Volumes, etc., of Ice and Sea-Water. THESE determinations were made in Hudson Strait (latitude 62° 33′ 45′′ north, longitude 70° 41′ 15′′ west), in an inlet having a width of a little more than half a mile. I am thus particular in giving the width, because in a very narrow tidal harbor, with the ice fast on either shore, the line of flotation of the ice would sensibly alter with a rising or falling tide. In this instance I was particular in watching for such a difference, under these opposite conditions; but, if present, it was insensible. The determination was made on Feb. 3, 1885, when the temperature of the air was-3° F.; for the water, 26°.7 F. A hole having been cut through the ice, of such a size as to pre vent any sensible error owing to capillarity, its thickness was found to be 2 feet 9.6 inches from surface to surface; on top of the ice was an estimated average depth of snow of 3 inches, of such a density that by weight it was equal to 1.1 inches of the ice: the total thickness of ice, or its equivalent, would therefore be 2 feet 10.7 inches. Of this amount, 32.5 inches were submerged; leaving, therefore, 2.2 inches of ice, or its equivalent, above the water-line. Therefore sea-water-ice floats with one part above the waterline and fourteen and eight-tenths below. Expressing the volume of a given quantity of sea-water by unity, its volume, when converted into ice, would be 1.0634; and their densities as 0.922 to 1.000. W. A. ASHE. The Observatory, Quebec, June 24. Death of W. O. Ayres, M.D. THE death of Dr. W. O. Ayres, one of the early members of the California Academy of Sciences, has recently been made known. He was specially interested in the study of ichthyology, and for many years after his arrival in California, in the intervals of an extensive medical practice, contributed to this department of natural history by his investigations of and publications upon the fishes of California. At the first meeting of the academy of which there is any published record, Sept. 4, 1854, he presented descriptions of two new species, Labrus pulcher and Hemitripterus marmoratus, which still stand, though the generic status has been modified, — now Harpe pulchra and Scoranichthys marmoratus. His contributions to the ichthyological knowledge of the Pacific coast were frequent for many years, especially from 1854, as above, to the year 1863. His scientific inquiries sometimes extended, though rarely, towards other forms of animal life. He returned to his native State, Connecticut, about 1872 or 1873. His services to the cause of science on the Pacific coast in those early days entitle him to grateful remembrance. U. S. Nat. Mus., June 28. Cause of Consumption. R. E. C. S. THE experimental together with the clinical study of tuberculoIsis has established the view that there are three factors in its causation : First, The presence of the parasite, the tubercle-bacillus, as a pathogenic element. This factor is necessary for the production of the disease. Second, Heredity figures as a prominent element in about thirty per cent of the cases ordinarily met with. Third, Mal-hygienic and debilitating agents, such as foul air, sedentary occupations, violations of the laws of health, and diseases, have a powerful effect, by impairing the nutrition, in developing the disease. Heredity and lowered vitality cannot of themselves produce tuberculosis, but clinically they play an important rôle as factors by rendering the individual more vulnerable to bacillary influence. FRANK DONALDSON, M.D. Baltimore, Md., June 29. Volapuk. YOUR correspondent, H. T. P.,' in your issue of the 24th of June, asks for information about Volapük. I can refer him to a most interesting article upon this subject, which appeared in the Bulletins de la Société d'Anthropologie de Paris, 1885, pp. 317 – 321. The article is by M. Kerckhoffs, who has published the following work, Cours Complet de Volapük,' par A. Kerckhoffs (Paris, 1886), and contains a sketch of the structure of the language and some interesting information about its prospects, progA. F. CHAMBERLAIN. ress, etc. Toronto, June 28. Queries. 7. DEATHS AND THE TIDE. —A physician living near the sea states that during the past five years he has noted the hour and minute of death in ninety-three patients, and every one has gone out with the tide, save four who died suddenly by accident. Is there any other evidence to sustain this statement ? — D. BOOK-NOTES. SCIENCE. AN ILLUSTRATED WEEKLY JOURNAL. THE bridge. OFFICERS AND DIRECTORS.-D. C. GILMAN, of - E. & F. N. Spon, New York, announce as in preparation Hot-Water Supply, a Practical Treatise upon the fitting of HotWater Apparatus for Domestic and General Purposes,' by F. Dye; The Kitchen Boiler and Water Pipes, a few Words on their Arrangement and Management, more Especially their Treatment during Frost and how to avoid Explosions,' by H. Grimshaw; and 'Notes on Concrete and Works in Concrete, Especially written to assist Those engaged upon Works,' by John Newman; and as just published, Buchanan's Tables of Squares, containing the Squares of Every Foot, Inch, and Sixteenth of an Inch between One-Six-SUBSCRIPTIONS.-United States and Canada, $3.50 a year. teenth of an Inch and Fifty Feet,' By E. E. Great Britain and Europe, $4 a year. Buchanan. The author worked these tables up for his own use in calculating, and, after having had them in almost constant service for six months, determined to have them printed, thinking that they might be of as much benefit to others as they are to him. . - Under the title of Village Types,' Julian Hawthorne will present, in The American Magazine for August, sketches of the more noted characters that are usually to be found in our small rural communities. - Recent methods of education form the subject of an essay by Col. I. Edwards Clarke, to appear in the next number of The American Magazine. Calendar of Societies. Natural Science Association, Staten Island. June 11.-William T. Davis, On the discovery, on May 29, of Clematis ochroleuca growing on a Sand-Dune; James Raymond, On Additions to the List of Birds known to breed on Staten Island; Arthur Hollick, On an Additional Oak for Staten Island; Dr. Carroll, Exhibition of a Calcite Crystal containing a Small Bubble. Publications received at Editor's Office, June 13-25. BERRY, J. J. How can the mortality of consumption be reduced? Manchester, N.H., J. B. Clarke, pr. 15 P. 12°. pl. CRAIG, J. E. Azimuth. New York, Wiley. 107 P., LEVEY, C. L. Electric light primer. New York, The MOONEY, J. The medical mythology of Ireland. Phila delphia, MacCalla & Co., pr. [31] p. 8°. SCIENCE," 47 Lafayette Place, New York. ADVERTISING RATES: $30 00 1 Page 1 time 1⁄2 Page 1 time Page 1 time 18 00 10 00 500 Importer, Manufacturer and Wholesale Dealer in all kinds of MUSICAL MERCHANDISE, MUSICAL BOXES, BAND STRATTON'S CELEBRATED RUSSIAN GUT For small advertisements the rate will be 15 cents Advertisements must be acceptable in every respect. as long as advertisement continues. FOR DYSPEPSIA, Nervousness, Weakened Energy, Horsford's NEWARK merchant and manufacturer and New Jersey RUMFORD CHEMICAL WORKS, work entrusted to us will be POHLMAN, J. The human teeth viewed in the light of evolution. Buffalo, Bigelow Bros. [6] p. 8°. SEYBERT Commission for investigating modern spiritualism, preliminary report of. Philadelphia, Lippincott. 159 p. 12°. TOWNE, E. C. Electricity and life: or, The electro-vital theory of nature. Cambridge, C. W. Sever. 32 p. 12°. U. S. GEOLOGICAL survey, topographical maps of portions of Texas, Missouri, and Arizona. 13 maps. 42 by 50.5 cm. Washington, Government, 1887. UNITED STATES, Tenth Census of the, 1880. Vol. xii. Part ii.: Mortality and vital statistics. Washington, Government. 803 p., plates and diagrams. 4°. WASHBURN observatory of the University of Wisconsin, Madison, State. publications of the. Vol. v. The Caligraph Writing Machine "How to Strengthen the Memory." Rev. E. L. Kelly, of Paterson, N. J., writing of Dr. Holbrook's book, "How to Strengthen the Memory; or, Natural and Scientific Methods of Never Forgetting," says; "I have read this treatise, this gem, and find a mine of wealth hidden in its pages. By it I was enabled last evening to learn the poem Stabat Mater,' in Latin. It took a little time, but the results were marvelous. Catalogue and prospectus free. Mailed to any address on receipt of $1, by M. L. HOLBROOK CO., 13 Laight St., New York. Mann's Reference Indexes. If you want to learn any thing about ANY SUBJECT send inquiry, with fifty (50) cents for estimate of cost of answer, to B: PICKMAN MANN, WASHINGTON, D.C. Transcripts and translations furnished. Explanatory circulars free. JAMES MCCREERY & CO. INVITE PARTICULAR ATTENTION TO THEIR GOODS SUITABLE FOR SUMMER VACATION WEAR. THE POPULAR KNITTED TUXEDO SUIT FOR LADIES, MISSES AND CHILDREN HAS NO EQUAL; IT IS LIGHT IN WEIGHT, FASHIONED FOR COMFORT, AND ADAPTED FOR THE SEA-SHORE, YACHTING AND LAWN TENNIS. IT CONSISTS OF A SKIRT, BLOUSE, CAP AND SASH, COMPLETE AND READY TO PUT ON WHEN DELIVERED TO THE CUSTOMER. THE ONLY GENUINE LIQUID GLUE GENUINE'S UNEQUALLED for CEMENTING, IS MADE BY THE COLD MEDALS. Gloucester, Mass PAGES DEODY FOR USE FOR MEN AND BOYS THERE IS A These glues are used in the Smithsonian Institute VERY LARGE ASSORTMENT OF THE at Washington for all its work of mounting speciFAMOUS MACKENZIE FLANNEL NEG- ment Buildings, by the Pullman Palace Car Co., mens-by the Government Arsenals and DepartMason & Hamlin Organ and Piano Co., and by LIGE SHIRTS, AS WELL AS MANY thousands of first-class manufacturers and mechanOTHER KINDS OF WHITE AND COL-ies throughout the world, for all kinds of fine work. Pronounced STRONGEST ADHESIVE KNOWN. ORED FLANNEL SHIRTS AND WAISTS. Sold in tin cans for mechanics and amateurs, and in bottles for family use. The total quantity sold between Jan., 1880, and Jan., 1885, in all parts of the world amounted to over 32 MILLION BOTTLES. Ве sure and get the genuine LePage's made only by RUSSIA CEMENT CO. BROADWAY AND ELEVENTH ST., The American Investment Company, of Emmettsburg, Iowa, with a paid-up capital of $600,000, surplus $75,000, offers first Mortgage Loans drawing seven per cent., both Principal and Interest fully guaranteed. Also 6 per cent. 10-year Debenture Bonds secured by 105 per cent. SUCCESSORS TO of first Mortgage Loans held in trust by the Mer- W. H. WALMSLEY & CO. cantile Trust Company, N. Y. 5 per cent, cerWrite tificates of deposit for periods under one year. for full information and references to the company at 150 Nassau St., N. Y. A. L. Ormsby, VicePres. and General Manager. DIAMONDS. A very large stock and great variety of diamonds constantly on hand. An assortment will be sent for examination in this city or vicinity when reliable parties desire it. WALTHAM WATCHES, RICH JEWELRY. FRENCH MARBLE CLOCKS, BRONZES, STERLING SILVERWARE, ETC. 2 MAIDEN LANE, N. Y. R. & J. BECK, 1016 Chestnut Street, Phila. Microscopes and all Accessories and Apparatus. Photographic and Photo-Micrographic Apparatus and Outfits. Spectacles, Eye Glasses, Opera and Marine Glasses, etc., Illustrated Price List mailed free to any adin corresponding with us. STUART & SHEPARD. dress. Mention SCIENCE 1 The Science Company, Publishers, 47 Lafayette Place, New York. London agent: G. E. Stechert, 26 King William St., Strand. JUST PUBLISHED. THE GRAPHICAL STATIS OF MECHANISM, A GUIDE FOR THE USE OF MACHINISTS, ARCHITECTS AND ENGINEYOR By GUSTAV HERRMANN, Professor in the Royal Polyte y Translated and Annotated by A. P. SMITH, A TEXT BOOK FOR TECHNICAL SCHOOLS. Aix-La-Chapelle. CONTENTS: 1. The Efficiency of Mechanisms. § 2. The Equilibrium of Mechanisms. 3. Sliding Friction. Electricity Treated Experimentally. For the use of Schools and Students. By LINNEUS CUMMING, M.A., late Scholar of Trinity College, Cambridge, Assistant Master in Rugby School. New Edition. With 242 Illustrations. Crown 8vo, $1.50. "Mr. Cumming has arranged a text-book of convenient size, embracing the elementary phenomena of electricity and magnetism, with reference to the latest theories, and the most improved forms of apparatus. The explanations are clear, the illustrations are good, and the questionsand examples are numerous, varied and educative. The book can be thoroughly recommended for class use, and for purposes of reference." -Schoolmaster. "The explanations are remarkably clear, and the text is further explained by many capitally executed diagrams."-Educational Times. "This is a good book. Mr. Cumming has succeeded in writing a work on what may be called an arithmetical basis, which can be understood by anyone with a fair knowledge of arithmetic. He works out many questions, and, what is very desirable, gives many examples to be worked out by the reader. The book should undoubtedly be in the hands of every electrical student or workman."-Iron. On the Conversion of Heat into Work. A Practical Handbook on Heat-Engines. By WILLIAM ANDERSON, M.Inst.C.E. With 55 Illustrations. Crown 8vo, 376 pages, cloth. Price $2.00. PREFACE.-The Council of the Society of Arts and Manufactures invited the Author of this work to deliver a course of lectures upon the conversion of heat into useful work; and in accordance with this resolution the course, which formed the foundation for the present work, was delivered in the Session of 1884-85 The object of the lectures was to popularize the doctrine that, in heat-engines, the work given out is due to the conversion of the molecular motion of heat into the visible motion which it was desired to produce; and further to illustrate, by numerous practical examples, the applicability of the doctrine of Sadi Carnot to defining the limits within which improvement in the economical working of heat-engines was possible. In the hope of making the modern views with respect to the action of heat more real and practical, the Author adopted the method of working out his investigations by means of numerical examples, and comparing the results with those obtained in actual practice. mal Friction. 5. Rolling Friction. 6. Chain The second part contains an enumeration of the applications to which these experiments have been put, and of others which might be carried out. The third part relates to phenomena observed with electric currents of high tension obtained by means described in the first part. The fourth part treats of analogies which these effects seem to present with many great natural phenomena, and the inferences drawn from them in order to explain these phenomena. The fifth part embraces the description and study of the effects of a new apparatus, by means of which we have tried to transform, in the most complete manner possible, dynamic into static electricity, distinguished by the name of rheostatic machine. The sixth is devoted to a concise enumeration of analogies which the electrical phenomena present with effects produced by mechanical actions, and to the inferences drawn from them as to the nature of electricity. Magneto and Dynamo-Electric Machines, with a Description of Electric Accumulators. A Practical Handbook, with use of the German of Glacer de Cew 2d Edition, enlarged. With a Preface and an Additional Chapter on the latest Types of Machine. By W. B. ESSON, M.S.T.E. With 99 Illustrations. Crown 8vo, pp. xi.-312, cloth, $3. Notes Embodying Recent Practice in the Sanitary Drainage of Buildings, with Memoranda on the Approximate Cost of Plumbing IN PRESS. 8vo, CLOTH. ILLUSTRATED. ABOUT 600 pp. ORGANIC ANALYSIS: A MANUAL OF THE DESCRIPTIVE AND ANALYTICAL CHEMISTRY OF CERTAIN CARBON COMPOUNDS IN COMMON USE. For the Qualitative and Quantitative Analysis of Organic Materials; Commercial and Pharmaceutical Assays; The Estimation of Impurities under Authorized Standards; Forensic Examinations for Poisons; and Elementary Organic Analysis. By ALBERT B. PRESCOTT, Director of the Chemical Laboratory in the University of Michigan, Author of "Outlines of Proximate Organic Analysis," "Qualitative Chemical Analysis," Etc. D. VAN NOSTRAND, Publisher, W. H. FARRINGTON, Agent, 23 Murray and 27 Warren Sts., N. Y. GUSTAV E. STECHERT, 828 Broadway, New York. Importer of Scientific Books and Periodicals. Branches: Leipzig, Hospital Str. 16; London. 26 King William Str., Strand. The Travelers Insurance Company of Hartford, Conn., organized 1864, issues both Life Policies and Accident Policies. Only large accident company in America. Only $5 a year to professional and business men for each $1,000 insurance, with $5 weekly indemnity. Has paid policy-holders nearly $11,000,000. All policies non-forfeitable. All claims paid, without discount, and immediately on receipt of satisfactory proof. MAP-MAKING. The American Investment Company, SCIENCE. AN ILLUSTRATED WEEKLY JOURNAL. THE SCIENCE COMPANY, OWNERS AND PUBLISHERS. OFFICERS AND DIRECTORS.-D. C. GILMAN, of Vice-President: GARDINER G. HUBBARD, of Washington Baltimore, President; SIMON NEWCOMB, of Washington, ALEX. GRAHAM BELL, of Washington; O. C. MARSH. of New Haven; J. W. POWELL. of Washington; W. P. TROWBRIDGE. of New York; S. H. SCUDDER, of Cambridge. SCIENCE appears every Friday. Volumes begin in July and January. Communications will be welcomed from any quarter. Rejected manuscripts will be returned postage accompanies the manuscript. to the authors only when the requisite amount of Address all correspondence to SCIENCE," Nervousness, Weakened Energy, INDIGESTION, Etc. of Emmettsburg, Iowa, with a paid-up capital of FOR DYSPEPSIA, $600,000, surplus $75,000, offers first Mortgage Loans drawing seven per cent., both Princi- Mental and Physical Exhaustion, pal and Interest fully guaranteed. Also 6 per cent. 10-year Debenture Bonds secured by 105 per cent. first Mortgage Loans held in trust by the Mercantile Trust Company, N. Y. 5 per cent. certificates of deposit for periods under one year. Write for full information and references to the company at 150 Nassau St., N. Y. A. L. Ormsby, VicePres. and General Manager. of DIAMONDS. All publishers or others desiring to have maps made, it either from relief plates or by carefully made under the Any A very large stock and great variety of diamonds constantly on hand. An assortment will be sent for examination in this city or vicinity when reliable parties desire WALTHAM WATCHES, RICH JEWELRY, FRENCH MARBLE CLOCKS, BRONZES, STERLING SILVERWARE, ETC. 2 MAIDEN LANE, N. Y. STUART & SHEPARD. LEPAGENUINE S QUID GLUE THE ONLY GENUINE THE ESTED TO 1600 LBS. TO SQ INCH Used by thousands of first-class Manufacturers RUSSIA CEMENT CO., Sample by mail se: stamps. These glues are used in the Smithsonian Institute at Washington for all its work of mounting speel mens-by the Government Arsenals and Department Buildings, by the Pullman Palace Car Co., Mason & Hamlin Organ and Piano Co., and by thousands of edit-first-class manufacturers and mechanics throughout N. D. C. HODGES, the world, for all kinds of flue work. Pronounced STRONGEST ADHESIVE KNOWN. Sold in tin cans for mechanics and amateurs, and in bottles for family use. The total quantity sold between Jan., 1880, and Jan., 1885, in all parts of the world amounted to over 32 MILLION BOTTLES. Be sure and get the genuine LePage's made only by RUSSIA CEMENT Co. NEW MAGAZINE-THE SWISS Devoted to spreading a love of CROSS by HARLAN H. BALLARD, President of the Agassiz Association, and succeeding St. Nichols as the official maga zine of that body. $1.50 a year. Sample copy 10 cents, or 25 cents for trial subscription for 3 months. N. D. C. HODGES, PUBLISHER, Mention this magazine 47 Lafayette Place, New York. Horsford's ACID PHOSPHATE. A liquid preparation of the phosphates and phosphoric acid. Recommended by physicians. It makes a delicious drink. Invigorating and strengthening. Pamphlet free. For sale by all dealers. RUMFORD CHEMICAL WORKS, Providence, R. I. BEWARE OF IMITATIONS. |