Diagram 5. By the first experiment I will try to show you how the space surrounding a conductor connected to a source of high-pressure elec Testing of Dielectric. tricity is, so to speak, filled with electric stresses, that become visible when a vacuum tube is brought near the conductor. This experiment was shown here by Nikola Tesla in connection with his lecture on alternate currents of high frequency; but I want to show you that high tension and low frequency produce the same effect. The next experiment was suggested by Dr. Obach, and the apparatus employed in it is shown in Diagram 5. A copper conductor (thickly insulated with indiarubber) is placed in a brass tube, and the annular space between them is filled with coloured water which communicates with a vertical glass tube inserted in the centre of the horizontal brass tube. One conductor from the high-tension transformer is connected to the insulated copper conductor, and the other to the brass tube. Under these conditions no current passes, but the electric stress heats the insulating material, which shows itself by the rise of the coloured liquid in the glass tube. Werner Siemens called attention to this phenomenon in a paper contributed to Poggendorf's Annalen in 1857, in which he communicated a series of experiments on electrostatic induction, proving, as he expressly stated, the correctness of Faraday's theory of molecular induction. Not very long ago Signor Riccardo Arno showed that a cylinder of insulating material, brought under the influence of a rotary field and suitably suspended, would commence to revolve, thus showing that molecular movement was set up in it. He produced this effect by means of an apparatus, a copy of which you see before you. A hollow cylinder of gutta-percha is suspended on the point of a needle, so that it can be made to turn with very little friction. Around it are placed four vertical metal strips to which the high-tension current is brought, as shown in Diagram 6. Between the two terminals of the high-tension circuit, a connection is made by an inductionless resistance in the shape of a U-tube filled with water and a condenser. Two of the metal strips opposite each other are joined to the ends of the inductionless resistance and the other two strips are connected to the condenser. In this way there is a difference of a quarter of a phase between the two currents, and a rotating field is produced, which causes the cylinder to revolve on account of the electrical hysteresis set up. When the current is reversed the cylinder revolves in the opposite direction. This result also obtains in the case of a glass beaker which is inverted and supported by a pinpoint. Wood, slate, and marble are usually reckoned to be insulating materials, but you will see that they do not offer a protracted resistance to a current of high potential. When the electric spark passes through marble it converts the carbonate of lime into quicklime, as can readily be shown by moistening the broken surface with phenolphthalein, which leaves the carbonate of lime white and colours the quicklime a beautiful pink colour. Even glass is pierced; and we must confess that at present we have no very reliable means of dealing with electricity of very high pressure. procuring the necessaries of life; and our experience shows that every time this has been done in the past, the burden of manual Enough has been shown, however, to prove that by utilising electricity we can extend the employment of natural forces for SWITCH labour has been lightened, and the comforts of mind and body have been made more accessible to the toiling multitude. In one word, all real and lasting progress is based on the practical application of scientific knowledge. [A. S.] GENERAL MONTHLY MEETING, Monday, February 6, 1893. SIR JAMES CRICHTON-BROWNE, M.D. LL.D. F.R.S. Treasurer and Vice-President, in the Chair. Frederick Canton, Esq. M.R.C.S. were elected Members of the Royal Institution. The Special Thanks of the Members were returned for the following Donations: Mrs. Bloomfield Moore Robert Wilson, Esq. John Bell Sedgwick, Esq. for carrying on investigations on Liquid Oxygen. £10 50 50 The Managers reported, that they had reappointed Professor James Dewar, M.A. L.L.D. F.R.S. as Fullerian Professor of Chemistry. The following Resolution from the Managers was read: Hodgkin's Trust. Having regard to the fact that the work of the Institution is devoted to the attainment of truth, and thereby constitutes in itself an investigation of the relations and co-relations existing between man and his Creator," Resolved, "That the income of the fund be devoted to that work, and that once in seven years a sum not exceeding 100 guineas be paid to some person, to be selected by the Managers, for writing an Essay showing how the work of this Institution has during the preceding period of seven years furthered the objects of the Trust." The PRESENTS received since the last Meeting were laid on the table, and the thanks of the Members returned for the same, viz.: FROM The Lords of the Admiralty-Nautical Almanac for 1896. 8vo. 1892. The Governor-General of India-Geological Survey of India. Records, Vol. XXV. Part 4. 8vo. 1892. The New Zealand Government-Statistics of the Colony of New Zealand for the year 1891. fol. 1892. Results of a Census taken in 1891. fol. 1892. Accademia dei Lincei, Reale, Roma-Atti, Serie Quinta: Rendiconti. Classe di Scienze fisiche matematiche e naturali. 2o Semestre, Vol. I. Fasc. 10-12. 8vo. 1892. Rendiconti, Serie Quinta, Classe di Scienze Morali, Storiche e Filologiche, Vol. I. Fasc. 9-10. Svo. 1892. Academy of Natural Sciences, Philadelphia-Proceedings, 1892, Part 2. 8vo. Astronomical Society, Royal-Monthly Notices, Vol. LIII. No. 1. 8vo. 1892. Bankers, Institute of Journal, Vol. XIII. Part 9. Vol. XIV. Part 1. 1892-3. 8vo. Ball, Sir Robert, LL.D. F.R.S. (the Author)—An Atlas of Astronomy. 8vo. 1892. British Astronomical Association-Journal, Vol. III. Nos. 1, 2. 8vo. 1893. British Museum Trustees—Catalogue of Marathi and Gujarati Books. By J. F. 8vo. 1892. Boston Public Library, U.S.A.—Bulletin, New Series, Vol. III. Nos. 1-4. 8vo. 1892-3. Canadian Institute-Transactions, Vol. III. Part 1. 8vo. 1892. Chemical Industry, Society of―Journal, Vol. XI. Nos. 11, 12. 8vo. 1892. Chemical Society-Journal for Dec. 1892, Jan. 1893. 8vo. Cracovie, l'Académie des Sciences-Bulletin, 1892, Nos. 9, 10. 8vo. Crisp, Frank, Esq. LL.B. F.L.S. M.R.I.-Journal of the Royal Microscopical Society, 1892, Part 6. 8vo. Editors-American Journal of Science for Dec. 1892 and Jan. 1893. 8vo. Analyst for Dec. 1892 and Jan. 1893. 8vo. Athenæum for Dec. 1892 and Jan. 1893. 4to. Author for Dec. 1892 and Jan. 1893. Brewers' Journal for Dec. 1892 and Jan. 1893. 4to. Chemical News for Dec. 1892 and Jan. 1893. 4to. Chemist and Druggist for Dec. 1892 and Jan. 1893. 8vo. Electric Plant for Dec. 1892 and Jan. 1893. 8vo. Electricity for Dec. 1892 and Jan. 1893. 8vo. Engineer for Dec. 1892 and Jan. 1893. fol. Engineering for Dec. 1892 and Jan. 1893. fol. Horological Journal for Dec. 1892 and Jan. 1893. 8vo. Industries for Dec. 1892 and Jan. 1893. fol. Iron for Dec. 1892 and Jan. 1893. 4to. Iron and Coal Trades Review for Dec. 1892 and Jan. 1893. 4to. Lightning for Dec. 1892 and Jan. 1893. 8vo. Monist for Dec. 1892 and Jan. 1893. 8vo. Open Court for Dec. 1892 and Jan. 1893. 4to. Photographic Work for Dec. 1892 and Jan. 1893. 8vo. Surveyor for Dec. 1892 and Jan. 1893. 8vo. Telegraphic Journal for Dec. 1892 and Jan. 1893. fol. |