Sept. 9, 1880] 



NATURE 



447 



machine than hitherto constructed with either the Jaminor the 

 ordinary horse-shoe form. It is also more symmetrical hi 

 appearance, and occupies less space. 



With this machine I can heat to incandescence nineteen inches 

 of platinum wire by four turns of the handle, while to heat four, 

 teen inches of the same size wire by a machine having a Jamiu 

 magnet it took ten turns of the handle. 



Mr. Bottomley followed up his report with a paper On 

 the Elastic i/y of Wires. This paper related the effect of 

 adding loads gradually to a wire which carried a load, and which 

 was found to increase in the limit of breaking strain when longer 

 times were allowed to elapse betsveen the successive increments of 

 the load. A charcoal iron wire which bare a load of 41 lbs. 

 when suddenly loaded would support 52 lbs. after having borne 

 theloadof4i lbs. for 790 hours. Some remarks were made by Sir 

 W. Thomson and by Dr. Siemens, •\\ho referred to some recent 

 experiments made in Germany of the stretching of wires and 

 rods of steel, which tended to show that protracted tensile strain 

 affected the chemical condition in which the carbon of the steel 

 was combined with the iron in it. Mr. J. E. H. Gordon referred 

 to the connection between the mechanical and magnetic 

 properties of steel under different conditions. 



On the Comparison of Declination Magnctographs at various 

 Places, by Prof. W. G. Adams. — This paper was accompanied 

 by diagrams of simultaneous magnetic disturbances at St. 

 Petersburg, Kew, and Vienna, showing that many of the sudden 

 magnetic disturbances occur simultaneously over very gi-eat areas, 

 but that in some cases the variations were in opposite directions. 

 In the debate which followed Sir \Vm. Thomson spoke of these 

 observations as beginning to open out a glimpse of the truecau^e 

 of the magnetic storms. He observed that if similar records of 

 the other magnetic elements, inclination and intensity, could be 

 procured, we should know definitely whether these disturbances 

 were due to any changes of the magnetism of the earth itself, or 

 whether they were due to an external magnetic action. Mag- 

 netic observations had been going on for forty years, and it was 

 a reproach that more had not hitherto been done. He also 

 referred to the alleged connection between aurorte and magnetic 

 storms. Mr. J. Glaisher and Staff-Commander Creak mentioned 

 cases of sudden magnetic disturbances. Capt. Creak recalled 

 the observations of the Arctic expeditions of 1875-6, when a 

 deflection of 5° was observed within forty minutes, the Kew 

 records show ing synchronously a smaller fluctuation. He argued 

 that an observing station in a more northerly latitude was 

 necessary. Mr. \V. H. Preece recounted a magnetic and 

 electrical storm which affected Ireland and the west of England 

 on August 12. Magnetic disturbances always were accompanied 

 by earth currents which affect the telegraph-wires. The same 

 storm affected even the Atlantic cables and the Cape cable. He 

 lielieved they would be found to have affected the whole earth. 

 The electromotive force on this occasion, through the Atlantic 

 cable, was about as great as that of 300 Daniell's cell, or more 

 exactly one volt per 6'6 miles. Capt. Creak also exhibited the 

 new Admiralty charts of the magnetic variation for iSSo. 



Prof. G. H. Minchin read a communication On Photoelectricity, 

 He had oVjtained feeble currents from two silver plates coated 

 with sensitive films of iodide, chloride, or bromide of silver, 

 dipping into a common fluid, and then one of them exposed to 

 the light. He had also observed that preparations of fluorescent 

 and phosphorescent bodies upon silver plates acted similarly. 



Prof. Silvanus P. Thompson gave a paper On Electric Con- 

 vection Currents, pointing out their analogies with true conduc- 

 tion currents, and of currents of electrolytic conductivity in 

 respect of electro-magnetic phenomena. The application to 

 ring-figures produced by disruptive convection and by electrolytic 

 conduction was considered, and their deformation in the magnetic 

 field. It was pointed out that considerations of a similar nature 

 had been advanced by Prof. Ayi-ton at an earlier date. 



Experiments on Thin films of IVater, with regard to the 

 Absorption of Radiant Heat, by the Hon. F. A. R. Russell. — 

 The experiments, the general results of which are given below, 

 were made with the object of ascertaining the diathermancy of 

 water in very thin films, and these experiments afforded inciden- 

 tally an opportunity of observing the behaviour of films subject 

 to varying conditions. 



The arrangement of instruments was similar to that illustrated 

 at p. 3S3 of Prof. Tyndall's "Heat as a Mode of Motion." 

 The ui-truments used were : a dead-beat mirror galvanometer 

 and scale, a thermopile, and a screen. The soa|) film was carried 

 by a piece of a cork sole perforated by a hole slightly larger than 



the hole in the screen, about I \ inch in diameter. The sources 

 of heat were (l) a copper or iron ball heated from behind by a 

 small gas flame ; (2) a gas flame from a Bunsen burner and (3) 

 a hydrogen flame in air. 



The film was mostly made from a solution of about half a 

 drachm of shavings of Castile soap, dissolved five to fifteen 

 minutes in about five cubic inches of water, at 60° F. 



The film, soon after being placed perpendicularly at the orifice 

 in the screen, exhibited coloured bands, which descended in 

 regular succession until the last band appeared, which contained 

 a bright blue line. The descentof the bands continued at a 

 slackened rate till the grey, and finally the black, occupied a 

 portion of the upper half of the film, which half was alone 

 subject to experiment. A condition more or less of equilibrium 

 then prevailed, the tension of the black portion counteracting the 

 force of gravity. A light yellow or bronze was always the laft 

 colour to appear, and preceded the white or grey, which again 

 was succeeded by black. When there was any black in the 

 film, the bursting of the film was marked by a slight click or 

 snajiping sound. The best films lasted frequently between ten 

 and thirty minutes, and sometimes the black portion alone was 

 under observation fifteen or twenty minutes. 



The following table shows the absorption per cent, for each of 

 the three sources of heat, and the thickness of the film, as derived 

 from a table in Watt's "Dictionary of Chemistry," giving 

 Newton's thicknesses of thin films of air, water, and glass. A 

 table in Cooke's "New Chemistry" gives the thicknesses of 

 soap-films as considerably greater than those stated in Newton's 

 table. The "hght film" of Cooke corresponds to my "grey," 

 and his "grey " to my " fine grey." Newton's " white " con'e- 

 sponds to my "grey." The refractive index of the solution 

 irsed by me was I "34 and I '35, a little higher than that of pure 

 water. 



SECTION B— Chemical Scien'CE 



On the Influence of Water on the Union of Carbonic Oxide -with 

 Oxygen at a High Temperature, by Harold B. Dixon, M.A.— 

 The author obtained the curious result that a mixture of carbonic 

 oxide and oxygen in such proportions as to fnrm carbon dioxide, 

 when free, or nearly free, from water, does not explode, either 

 by a direct discharge from a Leyden jar or when sparks are 

 passed through it from a Ruhmkorff coil. By allowing a minute 

 portion of aqueous vapour to mix with the gases, explosion im- 

 mediately t.akes place on the passage of the spark. In presence 

 of a very small trace of water, combustion takes place, bv.t 

 slowly, not with explosive energy. The author suggests as an 

 explanation the following equations : — 



CO -f H.,0 = CO., 4- H2 

 Ho 4- O = H26. 



Prof. Williamson suggested that it would be interesting to 

 determine the inferior limit to the power of water vapour in 

 causing an explosion, and that Mr. Dixon would probably extend 

 his research in this direction. 



Prof. Harcourt pointed out that various other similar instances 

 are known, among others the impossibility of causing union of 

 calcium oxide and carbonic anhydride, in absence of water, and 

 the refusal of dry chlorine to act on hot sodium. 



Mr. Thomas noticed that in mixtures containing large amounts 

 of marsh-gas the presence of water vapour also influenced the 

 rapidity uf explosion. 



