the observer on a second vessel provided with similar terminal conductors to the first, but having a telephone instead of a dynamo, will be able to detect the presence of the other vessel even at a considerable distance. This idea has been tested on a small scale with very promising results. A small boat, containing an interrupter and several cells of Leclanché battery, was moored upon the Potomac River in charge of an assistant. I then proceeded down the river in another boat containing a telephone. The circuits were arranged as described above. At the farthest distance tried-which appeared from the map to be about one mile and a quarter-the sounds produced by the action of the interrupter were distinctly but feebly heard. The experiment was not so successful when tried in salt water. I have hitherto refrained from publishing these ideas, as Prof. John Trowbridge, of Harvard College, communicated to me a year or so ago a very similar method which had occurred to him independently, and which I hoped he would publish. As this has not been done, and as the whole subject appears to me to be of importance, I have, with the permission of Prof. Trowbridge, ventured to bring it before your notice. Prof. Trowbridge proposed to utilize his method as a means of preventing collisions in a fog. He believed that by suitable modifications the officers of a ship might not only be able to detect the presence of an approaching vessel before dangerous proximity had been reached but might also be able to determine its position. As Prof. Trowbridge himself is present it will be unnecessary for me to describe his method in detail. ON THE INTENSITY OF SOUND. II THE ENERGY USED BY AN ORGAN PIPE. By Prof. C. K. WEAD, University of Michigan, Ann Arbor, Mich. [ABSTRACT.] In a previous paper the subject of the energy of vibration in tuning forks has been considered; and now, passing to gaseous bodies, we have to consider the energy per second that must be communicated to an organ pipe to maintain its sound. The general method is that described by Mr. Bosanquet (Phil. Mag. 1872) but the experiments are much more accurate. I. Drawing a single stop on the organ eight keys were pressed and the volume of air used per second found: from this of course the leakage is deducted, and the product of the remainder by the pressure on the bellows gives the work done. This was repeated in various parts of the scale and with various stops. It is very clear from the results that the efficiency of pipes of different stops is very different, as organ builders well know, and that a reed pipe is far more efficient mechanically than a flue pipe. II. Drawing all the nine stops of the great organ and pressing a single key, we find the relative work done in different parts of the scale. The results may be well expressed by an exponential curve whose ratio is found by least squares to be .59 for the octave in most cases. But the common organ-builders' rule is to make the 17th pipe half the diameter of the first; assuming here an exponential series, the diameter of the pipe an octave above the first would be the 12 power of which equals .5946. We must conclude therefore that Töpfer's rule endorsed by Mr. Bosanquet, according to which the ratio should be exactly .50, is true neither theoretically nor experimentally. A PRELIMINARY NOTE ON THE ACTION OF ACIDS UPON IRON IN THE MAGNETIC FIELD. By Prof. EDWARD L. NICHOLS, University of Kansas, Lawrence, Kansas. [ABSTRACT.] WHEN iron in the magnetic field is destroyed by acids, a process is performed which may be considered equivalent to its withdrawal by mechanical means to a position of zero potential. Since in such a process energy must be expended, we might expect the heating effect of the reaction to differ within and without the field by an amount equivalent to the energy necessary to withdraw the iron mechanically to an infinite distance. The author has completed a series of preliminary experiments to determine the character and amount of this difference. An electro-magnet was placed with its poles beneath and in contact with the bottom of a small beaker. Within the beaker were placed five grs. of iron filings and 100 cc. of aqua regia. A sensitive thermometer served to show the temperature of the solution. It was found, contrary to expectation, that the rise of temperature was much greater when the magnet was in circuit than when it was not acting. For purpose of comparison the reaction was repeated many times alternately with and without the current, care being taken that the conditions save those due to magnetization were in all cases the same. The average rise of temperature in fourteen consecutive meas urements was: Magnet acting, 63.°7 Magnet not acting, 48.07 The author's assistant, Mr. W. S. Franklin, repeated these measurements with the calorimeter. The mean of ten measurements showed the number of thermal units per gramme of iron consumed, to be: Magnet acting, 1288.8 Calories. The heat produced in these reactions was less than that obtained by Andrews by the combustion of iron in chlorine (1745 calories). Whether the product is in both cases a mixture of Fe,Cl, and FeCl¿ the ferric salt predominating when the magnet is acting, or whether, as has been suggested to the author, new salts are produced under the influence of the magnet, further experiments must determine. LOCAL AND TOPICAL WEATHER CARDS. By W. M. DAVIS, Harvard College, Cambridge, Mass. By employing a method of graphic transference, described in Science, Apr. 4, 1884, two sets of cards are prepared: one'showing the various kinds of weather experienced at certain selected stations, as controlled by distance and direction from the temporary, dominating region of high or low pressure; the other showing the distribution of certain single features of weather gathered from many stations and grouped in their proper attitude with respect to centres of high or low pressure. The first of these serves to discover what modifications of the general weather forecasts are needed for the stations for which they are applied. The second illustrates the limitation of certain phenomena, such as tornadoes, to relatively small parts of their parent cyclones. ON A PROOF OF CONTACT THEORY OF ELECTRICITY. E. DOLBEAR, Tufts College, Mass. [ABSTRACT.] By Prof. A. PROOF Consists in employing a magneto telephone which is connected to a wire whose ends consist of plates of different metals, e. g., zinc and carbon, or copper. These plates are then made to touch each other. Each touch may be heard, and if one terminal of the wire vibrates, like the prong of a tuning fork, against the other terminal, the rate of the vibration can be heard; thus showing the electrification and discharge by contact. ON COMPARATIVE COST OF ELECTRIC LIGHT AND OXYCALCIUM LIGHT. By Prof. A. E. DOLBEAR, Tufts College, Mass. [ABSTRACT.] THE paper assumes an expenditude of 8 cu. ft. of oxygen per hour for oxycalcium light and the amount of energy represented by that amount of oxygen, compares the mechanical equivalent and horse power, representing 2.4 horse power, yielding, say, 200 candles. Same amount of electrical energy spent in arc, gives about 2000 candle power and in incandescent about 200. ELECTRIC DISCHARGES IN RELATION TO THE EQUILIBRIUM OF GASEOUS ATMOSPHERES. By Prof. JAMES DEWAR, Cambridge, Eng. [ABSTRACT.] THE experiments detailed in this paper had reference to the variation in the amount of acetylene synthetically produced under different conditions of pressure and electric discharge. TITLES OF OTHER PAPERS READ IN SECTION B. ON THE DISTRIBUTION OF POTENTIAL IN CONDUCTORS EXPERI ENCING THE ELECTROMAGNETIC EFFECTS DISCOVERED BY HALL. By Sir WILLIAM THOMPSON, University of Glasgow, Scotland. ON A STANDARD TANGENT GALVANOMETER. By Prof. SILVANUS THOMPSON, University College, Bristol, England. ON THE GOVERNMENT OF ELECTRIC MOTORS. By Prof. SILVANUS THOMPSON, University College, Bristol, England. CHANGE IN RAINFALL OF VIRGINIA. By J. R. PURDIE, M. D., Smithfield, Isle of Wight Co., Va. THE PRINCETON METEOROLOGICAL OBSERVATORY. By Prof. WILLIAM LIBBEY, jr., Princeton, N. J. A FORM OF APPARATUS FOR DETERMINING THE DIATHERMACY OF AIR AND GASES. By JOHN R. PADDOCK, Stevens Institute, Hoboken, N. J. A PROPOSED METHOD OF DETERMINING THE MAGNETIC DIP BY MEANS OF A MAGNETIC PENDULUM. By MARCUS BAKER, U. S. Coast and Geodetic Survey, Washington, D. C. DESCRIPTION OF A GALVANOMETER FOR DEMONSTRATING THE INTERNAL CURRENT TRANSMITTED THROUGH THE LIQUID WITHIN A VOLTAIC CELL. BY CONRAD W. COOKE, C. E., Westminster, Eng. THERMAL BELTS. By Prof. J. W. CHICKERING, jr., Deaf Mute College, Washington, D. C. GEOMETRICAL METHODS IN THE THEORY OF REFRACTION AT ONE OR MORE SURFACES. By Prof. JAMES LOUDON, University College. Toronto, Canada. SOME RELATIONS OF POSITIVE AND NEGATIVE ELECTRICITY. By Dr. H. W. EATON, Louisville, Ky. A METHOD OF DISTRIBUTING WEATHER FORECAST BY MEANS OF RAILROAD TRAINS, ETC. By JOHN A. MILLER, Cairo, Ill. |