stiff mass, which is permeated throughout by zinc sulphate crystals and globules of mercury. If the sulphate, however, be moist, only zinc sulphate crystals are to be added; care must, however, be taken that these occur in excess and are not dissolved after continued standing. The mercury must, in this case also, permeate the paste in little globules. It is advantageous to crush the zinc sulphate crystals before using, since the paste can then be better manipulated. To set up the cell.-The containing glass vessel, represented in the accompanying figure, shall consist of two limbs closed at bottom and joined above to a common neck fitted with a ground glass stopper. The diameter of the limbs should be at least 2 cms., and their length at least 3 cms. The neck should not be less than 1.5 cms. in diameter. At the bottom of each limb a platinum wire of about 0.4 mm. diameter is sealed through the glass. To set up the cell, place in one limb pure mercury, and in the other hot liquid amalgam, containing 90 parts mercury and 10 parts zinc. The platinum wires at the bottom must be completely covered by the mercury and the amalgam, respectively. On the mercury place a layer 1 cm. thick of the zinc and mercurous sulphate paste described in 5. Both this paste and the zinc amalgam must then be covered with a layer of the neutral zinc sulphate crystals 1 cm. thick. The whole vessel must then be filled with the saturated zinc sulphate solution, and the stopper inserted so that it shall just touch it, leaving, however, a small bubble to guard against breakage when the temperature rises. Before finally inserting the glass stopper it is to be brushed round its upper edge with a strong alcoholic solution of shellac and pressed firmly in place. (For details of filling the cell, see Note B.) NOTES TO THE SPECIFICATIONS. (A) The mercurous sulphate.-The treatment of the mercurous sulphate has for its object the removal of any mercuric sulphate which is often present as an impurity. Mercuric sulphate decomposes in the presence of water into an acid and a basic sulphate. The latter is a yellow substance-turpeth mineral-practically insoluble in water; its presence, at any rate in moderate quantities, has no effect on the cell. If, however, it be formed, the acid sulphate is also formed. This is soluble in water, and the acid produced affects the electromotive force. The object of the washings is to dissolve and remove this acid sulphate, and for this purpose the three washings described in the specification will suffice in nearly all cases. If, however, much of the turpeth mineral be formed, it shows that there is a great deal of the acid sulphate present, and it will then be wiser to obtain a fresh sample of mercurous sulphate, rather than to try by repeated washings to get rid of all the acid. The free mercury helps in the process of removing the acid, for the acid mercuric sulphate attacks it, forming mercurous sulphate. Pure mercurous sulphate, when quite free from acid, shows on repeated washing a faint yellow tinge, which is due to the formation of a basic mercurous salt distinct from the turpeth mineral, or basic mercuric sulphate. The appearance of this primrose yellow tint may be taken as an indication that all the acid has been removed; the washing may with advantage be continued until this tint appears. (B) Filling the cell.-After thoroughly cleaning and drying the glass vessel, place it in a hot-water bath. Then pass through the neck of the vessel a thin glass tube reaching to the bottom to serve for the introduction of the amalgam. This tube should be as large as the glass vessel will admit. It serves to protect the upper part of the cell from being soiled with the amalgam. To fill in the amalgam, a clean dropping tube about 10 cm. long, drawn out to a fine point, should be used. Its lower end is brought under the surface of the amalgam heated in a porcelain dish, and some of the amalgam is drawn into the tube by means of the rubber bulb. The point is then quickly cleaned of dross with filter paper and is passed through the wider tube to the bottom and emptied by pressing the bulb. The point of the tube must be so fine that the amalgam will come out only on squeezing the bulb. This process is repeated until the limb contains the desired quantity of the amalgam. The vessel is then removed from the water bath. After cooling, the amalgam must adhere to the glass and must show a clean surface with a metallic luster. For insertion of the mercury, a dropping tube with a long stem will be found convenient. The paste may be poured in through a wide tube reaching nearly down to the mercury and having a funnel-shaped top. If the paste does not move down freely, it may be pushed down with a small glass rod. The paste and the amalgam are then both covered with the zinc-sulphate crystals before the concentrated zinc-sulphate solution is poured in. This should be added through a small funnel, so as to leave the neck of the vessel clean and dry. For convenience and security in handling, the cell may be mounted in a suitable case, so as to be at all times open to inspection. In using the cell, sudden variations of temperature should, as far as possible, be avoided, since the changes in electromotive force lag behind those of temperature. Respectfully submitted. HENRY A. ROWLAND, Chairman, HENRY L. ABBOT, GEORGE F. BARKER, CHARLES S. HASTINGS, ALBERT A. MICHELSON, CARL BARUS, Committee. The report containing the above specifications was accepted and unanimously adopted by the Academy. It was voted unanimously that the National Academy of Sciences, in accordance with section 2 of the act of Congress of July 12, 1894, entitled "An act to define and establish the units of electrical measure," does hereby prescribe the above specifications of details necessary for the practical application of the definitions of the ampere and volt called for by said act. It was also voted unanimously that these specifications be published by the sending, by the president, of a copy of the same to each House of Congress and to the Secretary of State, with the request to the latter that they be issued by the State Department; and, further, by the printing by the home secretary of the Academy of a suitable number of copies for public distribution. No further business was transacted, and the Academy adjourned to meet in Washington April 16, 1895. ANNUAL MEETING. [Held in Washington April 16 to 19, 1895.] The session was held in the National Museum, the president, Prof. O. C. Marsh, presiding. The following members were present during the session: Abbe, Abbot, Agassiz, Barker, Barus, Billings, Boss, Chandler (C. F.), Chandler (S. C.), Chittenden, Comstock, Cope, Gibbs (W.), Gilbert, Gill, Goode, Gould, Hague, Hall (A.), Hastings, Hill (G. W.), Marsh, Mendenhall, Michelson, Mitchell (S. W.), Morse, Newcomb, Powell, Remsen, Rowand, Walker, White. Thirty-two members were present in all. The president made a brief oral report. The home secretary submitted the following report for the past year: HOME SECRETARY'S REPORT. The general work of the past year has gone on as usual. The sixth volume of the memoirs of the Academy was finished and distributed in December, 1894. The annual reports for 1893 and 1894 have been printed during the present year and have been sent to members. The seventh volume of memoirs is now in the hands of the Public Printer. The contracts for the illustrations have been made and the printing will begin soon. The printing of the memoirs of the Academy and the annual reports have been ordered by act of Congress, so that the former delays will be avoided in future. The manuscript of Part III of the Proceedings of the Academy has been prepared and is ready for printing. This part will complete the first volume and brings the account of the Academy up to 1895. The Academy is much indebted to the Smithsonian Institution for the storage of its books and for sending out its publications. As the Institution needed the rooms occupied by the Academy, it was necessary to remove the books and records, and a division of books was made according to countries. The books are now packed away in 49 boxes, which are marked on the outside with the names of the countries sending the books. The report of the treasurer was presented, and here follows TREASURER'S REPORT. WASHINGTON, D. C., April 16, 1895. To the PRESIDENT NATIONAL ACADEMY OF SCIENCES. SIR: I have the honor to transmit herewith my financial report as treasurer of the National Academy of Sciences for the year ending April 16, 1895: |