460 



NATURE 



[April 6, 1876 



necessary either that the wires shall not touch each other, or that 

 if they do, no flow shall pass across the junction. This rule is 

 often overlooked, and the oversight has given rise in certain 

 cases to a notion of electrical "interference." The concluding 

 part of the paper has to do with the flow conditions when 

 fine poles are combined with point poles in a sheet, espe- 

 cially when point electrodes are introduced into a sheet wlien 

 a uniform current or "river" is flowing across the sheet. — Dr. 

 Guthrie then communicated a fourth paper on salt solutions and 

 attached water. It consists mainly of an account of an examina- 

 tion of the behaviour of a salt solution, when cooled below the 

 freezing point of water. Having shown in previous communica- 

 tions that every salt solution, when of a certain strength solidifies 

 as a whole, at a certain temperature as a cryohydrate, the present 

 research was directed to the determination of the temperatures 

 at which, (i) ice separates from solutions of strengths weaker 

 than the cryohydrate, and (2), the anhydrous salt or some 

 hydrate richer than the cryohydrate, separates from solutions 

 stronger than the cryohydrate. About twenty typical salts have 

 been examined in this manner, and curves were exhibited in 

 which the abscissae represent strengths, and the ordinates solidifi- 

 cation temperatures. All the curves have a similar character 

 and exhibit a point of contrary flexure, between the origin repre- 

 senting pure water at C C. and the cryohydrate. Between the 

 cryohydrate and the 0° C. degree of saturation, they are nearly 

 straight lines, and are continuous with the curves of solubility 

 above 0° C. The joint effect of two salts in depressing the 

 temperature of ice-formation was also examined. From previous 

 experiments the general law that the temperature of a freezing 

 mixture is identical with that of the solidification of the cryohy- 

 drate of the corresponding salt, appeai-ed not to be the case 

 with iodide of sodium. It now appears that this salt offers no 

 exception to the general law and that what was previously mis- 

 taken for the cryohydrate is really a sub-cryohydratesolidifying at a 

 higher temperature. Certain remarkable cases of supersaturation 

 were discussed which show that a solution may be supersaturated 

 in a 3-fold manner, (i) with regard to ice (2) with regard to a 

 salt, and (3) with regard to the cryohydrate of the salt. The 

 parallelism between a boiling saturated salt solution and a 

 glaciating one was pointed out. 



Paris 

 Academy of Sciences, March 27. — Vice-Admiral Paris in 

 the chair. — The following papers were read : — Influence of 

 variations of pressure on the Avorking of chronometers, by M. 

 Yvon Villarceau. — On the small movements of an incompres- 

 sible fluid in an elastic tube, by M. Resal. The velocity of 

 propagation of waves is equal to the square root of the product 

 of the coefficient of elasticity and the thickness of the tube 

 divided by that of the diameter of the tube and the density of 

 the liquid.— Observations of temperature at the Museum of 

 Natural History during 1875, with electric thermometers 

 placed in the air and in turf-covered and bare ground, by 

 iVl. Becquerel. The temperature was, on an average, some- 

 what higher in the turf-covered ground than in the bare 

 ground, and in the former it never descended below zero. — 

 On the comparative movements of the thermometer and baro- 

 meter during the commotion of March, 1876, by M. Sainte- 

 Claire-Deville. The periodic oscillation of the temperature 

 from 9th to I3ih March did not fail to be produced, and the 

 law of non-synchronic parallelism of temperature and pressure 

 is realised even in the most sudden variations of these two ele- 

 ments. — Kemz.x\isaf'i-opos of Mr. Lockyer's communication on new 

 lines of calcium, by M. Sainte Ciaire-Deville. In two neighbouring 

 groups of mineral substances, there are most frequently two 

 minerals belonging respectively to each, and characterised by the 

 same basic element. Now of all simple bodies it is calcium that 

 most commonly plays this double role. Is this connected with 

 its double behaviour under the influence of dissociants ? — Expe- 

 riments on the schistosity of rocks, and the deformations of 

 fossils correlative to this phenomenon ; geological consequences 

 of these experiments, by M. Daubree (first part). The press 

 used in these instructive experiments could give a total pressure 

 of 100,000 kilogrammes on the plates. — Reproduction of Ambly- 

 stoma observed in the museum, by M. Blanchard. The Ambly- 

 stonia of Mexico is the adult form of the AxolotI, and the fact 

 observed is important as disproving the idea of the sterility of 

 certain Batrachians in the adult state. — Continued observations 

 of solar protuberances during the second semester of 1875, by 

 P. Secchi. These comprise seven rotations. It is a period of 

 prolonged mininuuu ; the absolute minimum not yet reached 



(March). Protuberances varying from 2 or 3 one day to 10 or 

 12 the next. The hydrogenic flames were commonly straight, 

 though 2 or even 3 minutes in height (say 60 terrestrial dia- 

 meters) ; this indicates great tranquility. The chromosphere 

 was very low at the equator, but often reached a great height 

 at the poles (24 and 30 seconds). This is the effect of dis- 

 placement of maxima towards the poles. — Mr. Spottiswoode 

 was elected correspondent in the section of Geometry, in 

 room of the late M. Le Besgue. — Report on a memoir of M, 

 Bourgoin, entitled " Researches in the succinic series. " — Employ- 

 ment of coal-tar and of.sulpho-carbonates against Phylloxera, by 

 M. de la Vergne. — Analytic theory of the movements of Jupiter's 

 satellites, by M. Souillart. — Results of actinometric measure- 

 ments on the summit of Mont Blanc, by M. Violle. — Velocity of 

 thermal flow in a bar of iron, by M. Decharme. The times taken 

 by the flow to reach different points in the bar are direcily pro- 

 portional to the squares of the distances of these points from the 

 heated end ; or, the velocities of thermal flow are inversely pro- 

 portional to the squares of the distances. (The cooling is slower 

 than the heating). — Study on stratified light ; memoir by M. 

 Neyreneuf. — The elephants of Mont Dol ; organogeny of the 

 system of molar teeth of the mammoth, by M. Sirodot. — Photo- 

 micrographic researches on the trans' ormation of collodion in 

 photographic operations, by M. Girard. Microscopic examina- 

 tion of collodion enables one to know the nature of the layer and 

 to follow the reactions produced in photographic impression. — 

 On "communications at a distance by water-courses, by M. Bour- 

 bouze (sealed packet deposited in 1870). Lines are dispensed with, 

 and earth currents utilised. — On the conditions of immediate inte- 

 grability of an expression with ordinary differentials of any order, 

 byM. Pujet. — Impossibility of the equation .a;^ + y' + z' — o, by 

 M. Pepin. — On the exchange of ammonia between natural 

 waters and the atmosphere, by M. Schloesing. The ammonii 

 condensed by a given quantity of water increases rapidly with 

 diminution of temperature. It is a mistake to suppose the 

 ammonia of a cloud is condensed almost entirely ia rain. 

 — Sources of carbonic oxide ; new mode of preparation of 

 very concentrated formic acid, by M. Lorin. In this method 

 dehydrated oxalic acid is used in place of sulphuric acid, with a 

 formiate.— On the constitution of the excretory canal of the 

 hermaphrodite organ in Le2icochron candidissitna, Beck, and in 

 Bulhnus decollatus, Linn., by M. Dubrueil. — On the relations 

 between number of molar teeth in the dog and dimensions of 

 the bones of the face, by M. Toussaint. The normal formula 



for molar teeth of the dog is _, but in the extreme, dissimilar 

 7 



types of bulldog and greyhound the formulae of i or 2_ for 



7 6 



the former, and L. for the latter, are met with. One may 



9 

 follow the transformation of the formulae by examining inter- 

 mediate types. — Researches on the convergence and divergence 

 of formulae of Fourier's representation, by M, Paul de Bois 

 Reymond. 



CONTENTS - Page 



Pkeece's Telegraphy 441 



Musical Instruments at South Kensington (IVtiA J/tusira- 



iious) . 443 



Our Book Shelf :— 



Procter's " Non-Metallic Elements and their Compoundi "... 446 

 Letters TO THE Edit >K : — 



The Use of the Words "Weight" and "Mass."— J. T. Botto.m- 



LEY 446 



Burds as Astronomical Objects. — Prof. Alfred Newton, I<\R. S. . 447 



How Typhoid Fever is Spread. — Dr. £. Fkankland, F. R.S. . . 447 



Lisbon Magnetic Observations. — John Allan Bkoun, F. R.S. . 448 



The Early History of Continued Fractions. — Tho.mas MuiR . . 448 



The Dry River-beds of the Riviera.— He.\ry T. Wharton . . . 44S 



The Flame of Common Salt. — T. N. Mueller 448 



Our Astronomical Column : — 



Double Stars 449 



The Equator of Mars 449 



A Southern Comet (?J 449 



Hunterian Lectures on the Relation ok E.xtlnxf to Exisri.No 



Ma-mmalia, VL By Prof Flower, F. R.S 449 



On Repulsion Resulting From R.\diation. — Part IV 450 



Science IN Germany (^^'zV/j /t/usiraitou) 452 



The International Metric Co.m.mission at Paris. By H. W. 



CHitsHOLM 452 



Physical Science in Schools. By T. Wyles ; Dr. W. Marshall 



Watts 454 



Notes 455 



sociktiks and academies • 45^ 



