94 



NA TURE 



[May 24, 1894 



only a small diminaiion of resistance with increase of voltage. 

 For a sheet 6 mils thick the resistance between opposite faces 5J 

 inches diameter was of the order 30 megohms, and one speci- 

 men broke down at 1200 volts. The celluloid condensers used 

 in the experiments were found to discharge slowly at first, and 

 after a cer.ain time the deflection of the galvanometer became 

 rerersed, and attained a steady negative value. This the author 

 attributes to an E. M.F. of about 00006 volt between the mer- 

 cary and celluloid. Similar experiments on gutta-percha tissue 

 showed no such E. M.F. , and the "electrification " was normal. 

 The resistance usually attained a maximum for voltages between 

 600 and Soo. Although the tissue had a thickness of only 2 

 mils (0"co2 ■), it stood a pressure of 1200 volts, and offered a 

 resistance between circular faces 5i inches in diameter of about 

 3000 megohms. The opaque white spots seen in celluloid 

 under the microscope, led the author to test the behaviour of 

 mixtures of conducting and insulating materials. A strip of 

 gutta-percha was warmed, and coarse brass filings scattered 

 over it as thickly as possible. In spite of this the resistance was 

 practically infinite even when tested with 750 volts. .\ number 

 of rods were made from mixtures of brass and gutla-percha in 

 various proportions, and on testing these it was found that if the 

 weight of filings exceeded about twice that of the guttapercha, 

 the resisiance of a rod 20 inches long, ;,' inch diameter, was 

 small (sometimes a fraction of an ohm), whereas a slightly 

 smaller proportion yielded rods having resistances measured in 

 thousands of megohms. Such rods were found to be affected 

 by oscillating discharges in a manner similar to Prof. Minchin's 

 "impulsion" cells and M. Branly's tubes of filing---. Experi- 

 ments were also made on the behaviour of such rods when 

 subjected to high alternating pressures. This caused small local 

 arcs to form along the rods, but did not permanently destroy 

 their high resistance. — In connection with Mr. Applcyard's 

 paper, a note on the behaviour of certain bodies in presence 

 of electromagnetic oscillations, by Prof. G. M. Minchin, 

 was read by Mr. Elder. Referring to the employment of 

 impulsion cells, metallic films, &c., for detecting the modes of 

 electrom.Tgnetic vibrations, he says that so far the physical state 

 of such bodies are too variable to be of service. Metallic sur- 

 faces formed by embedding fine n-etallic powders in films of 

 gelatine, shellac, or sealing-wax, are, as described in a previous 

 communication to the Society, found to act as insulators, but 

 become conducting when subjected to strong electromagnetic 

 disturbances. After a current has once passed through such a 

 film its resistance is changed by very feeble impulses, whereas 

 previously it failed to respond to strong ones. On breaking 

 contact by removing the electrode from the surface, the film 

 loses its conductivity, the time necessary to d^ this depending 

 rn the hardness of the matrix. The resistance of a film contain- 

 ing tin powder, measured between the rounded tips of two pla- 

 tinum wires, i cm. apart, varied under the electromagnetic im- 

 pulses from infinity to 130 ohms. In conclusion, the author points 

 out that with films and tubes the whole phenomenon relates to 

 change of resistance, whereas impulsion cells may have currents 

 from external sources passing through them whilst in either the 

 sensitive or insensitive state.'.— Mr. Bright and Mr. I'.nright 

 asked questions as to the electrification of gutta-percha, and the 

 bridge connections in the resistance tests of the semi-conducting 

 ro<ls respectively, to which Mr. .Apjileyard replied. 



Royal Meteorological Society, May 16.— Mr. R. 

 Inwards, I'tesident, in the chair.— .Mr. W. Ellis, F.R.S., 

 read a paper on the relative frequency of different velocities 

 • of wind, in which he discussed the anemometer records of 

 the Greenwich Observatory for the five years 1S88 1S92, with 

 the view of asccitaining the number of hours during which 

 the wind Mew, with each of the different hourly velocities 

 experienced during the period. The results of this discussion 

 show that the wind blew for the greatest number of hours with 

 the hourly velocities often and eleven miles.— Mr. W. Marriott 

 Jjavc an account of a series of observations on the audibility of 

 " Big Ben" at West Norwood, which he had carried on for a 

 period of five years. The clock tower at Westminster is five 

 and a half miles distant from the point of observation in a 

 north-liy-wcst direction. The large bell "Big Ben" was 

 designed by Lord Grimthorpe, and was cast in 1S58 ; its weight 

 is about fouitccn tons. It is 9 ft. 5J ins. in diameter, and 

 93 ins. in thickness, its lone being E. The observati ms were 

 976 in number, and were made at the hours ol 9 a.m. and 9 

 p.m. The l>ell could be heard more frequently in the evening 

 than in the morning, and on Sunday.s it was more frequently 



NO. 1282, VOL. 50] 



audible than on week-days. The direction of the wind most 

 favourable for hearing "Big Ben" was between west and 

 north. The observations were also discussed in relation to 

 temperature, moisture, cloud, and barometric pressure. — .\ 

 paper by Mr. .\. W. Moore was also read on earth tempera- 

 tures at Cronkbourne, Isle of Man, iSSo 18S9. 



Royal Microscopical Society, April 18.— Mr. .\. D. 

 Michael, president, in the chair. — Dr. W. H. Dallinger directed 

 attention to a stereoscopic photomicrograph of Heliopelta, 

 which had been presented to the Society by Dr. \V. C. Borden, 

 of New York. — Dr. Dallinger read a short paper from Dr. 

 H. G. Piffard, in reference to a method which he had adopted 

 for the examination of some of the old immersion objectives. — 

 Mr. I. \V. Brown exhibited a "homemade" microscope.^ 

 Prof. F. J. Bell read a letter from M. C. I. Pound, describing the 

 laboratories of the Stock Institute of Queensland, which had 

 recently been instituted for the purpose of investigating the 

 nature and causes of animal diseases in that colony. — Mr. I. G. 

 Grenfell read a paper on the tracks, threads, and films of oscd- 

 latorise and diatoms, illustrating his subject by diagrams and 

 specimens. Mr. T. Comber and the President made some 

 remarks on Mr. Grenfell s paper. 



Paris. 

 Academy of Sciences, May 15.— M. I.cewy in the chair.— 

 On the inlluence of bending in telescopes mounted as coude 

 equatorial?, by M.M. Lnwy and Puiseux. — Researches oa 

 the augmentation of crops by introduction into the soil of large 

 quantities of carbon bisulphide, by M. .-Mnie Girard. The 

 author shows that, for at least two years after treating soils 

 with carbon bisulphide, wheat, oats, beetroot, potatoes, and 

 clover yield much heavier crops than on soil not treated. He 

 traces the increased production rather to the destruction of 

 insect pests than to any action on parasites belonging to 

 the vegetable kingdom. — Observation of Tempel's comet 

 (1S73 II.) made at .\lgiers Observatory. A lelegraphic 

 despatch transmitted by M. Tisserand. — On the periodic comet 

 Tempel (1873 Il.\ by M. L. Schulhof — Observations of 

 comet Denning (1894, March 26) made at Toulouse Observa- 

 tory, by M. E. Cosserat. — Observations of Gale's comet 

 (1894, April 3) made at Lyons Observatory, by M. J. 

 Guillaume.— Ol>servations of the same comet made with 

 the coude equatorial at Lyons Observatory, by .M. f. 

 Le Cadet. — Graphic cphemerides giving the co-ordin.ii 

 of the stars for the purposes of navigation, by M. Lo 

 Favc. — On the equations of mechanics, by AI. Wladim ; 

 de Tannenberg. — Determination of the relative intensity i 

 gravity, made at Joal (Senegal) by the expedition sent out by 

 the Bureau des Longitudes to observe the total eclipse of the 

 sun on .\pril 16, 1S93, by M. G. Bigouidan. Taking ;,■ = n*^: 

 at Paris, at Joal the mean value of 1,', reiluced to sea-lev< 

 is 978 437. This result confirms Dcfforgc's law that ^ I 

 a characteristic value for the littoral of the same s> 

 of which the variation follows exactly Clairaut's law of the sii 

 squared of the latitude. — On the physical properties of | 11 

 nitrous oxide, by M. P. Villard. The author describes :' 

 preparation of the pureg.is by a liquefaction method, and com- 

 pares the densities of the liquid and its vapour from o^ to 36°'3. 

 lie finds the critical temperature of the pure gas to be jS'S as 

 compared with Dewar's value, 35 4, and Janssen's 36 '4. The 

 critical volume, density, and pressure are respectively 000436, 

 o 454, and 775 atmospheres. — On the stability of dilute solir 

 tions of corrosive sublimate, by M. Leo Vignon. The stability 

 depends on the absence of alkaline matter which may be present 

 in the water used or derived from the air or the glass of the 

 containing vessel. On the chemical character and constitution 

 of ethylic acetoacetate, by M. de Forcrand. From a con- 

 sideration of thermal data, the author concludes that ethylic 

 acetoacetate most nearly resembles phenols, that it is neiili' 

 an acid nor a ketone, but a tertiary alcohol of a special tji 

 and should be represented by the formula 



CH3,C(0!I):CH.C00Et. 

 — Comparative study of the isomeric nitrobencoic acids, by M 

 Oechsner de Coninck.— The Diptera parasitic on Acridiai. 

 viviparous .Muscidx, <) lan'es farcophai;es. Aptenia and p.n 

 sitic castration, by M. J. Kiinckel d'llerculais. — On the fixi: . 

 of race in the cultivated mushroom, by MM. Costanlin and 1 

 Matruchot. The peculiarities distingui-hing the varieties recoj; 

 nised by mushroom growers are hereditary. -Remark concern 

 ing a recent communication, by ,VI. Issel, on the Zante earth- 



