142 



NATURE 



[June 7, 1883 



The Beibliilter to part 4 contains papers on the necessity of 

 introducing certain modifications into the study of mechanics, 

 ar.d eliminating diverse problems from them, by Yvon Villar- 

 ceau. — On the influence of temperature on manifestations of 

 molecular energy, by A. Millar. — On the inner pressure and 

 energy of superheated vapours, by G. Schmidt. 



Journal de Physique Theorique it Appliquee, April, 18S3. — 

 Methods for determining the ohm, by Marcel Brillouin. — On the 

 solidification of phosphorus and other substances in supervision, 

 by M. D. Gerne?. — On the theory of colourless curves in double 

 refractive crystals, by J. Mace de Lepinay. — A new hygrometer 

 condensing internally, described and figured by A. Crova. — A 

 new electrocapillary translator, described and figured by E. 

 Debrun. — On the reading of a system of two electrodynamic 

 machines, by A. I'otier. 



Reinie Internationale des Sciences, February, 1883, contains 

 articles : — On the contagiousness of tubercle. — On the Khouds, by 

 Elie Reclus. — On the dangerous properties of finely-divided 

 coal-dust, by Prof. Abel. — On the adulteration of food in Paris, 

 by M. Egasse. — Medical anthropometry from the point of view 

 of aptitude for military service, by M. Jansen. — Proceedings of 

 the Academy of Sciences, Paris. 



Journal of tin- Asiatic Society 0/ Bengal, Vol. li. Part 11, 

 No. 4, 18S2, contains : — On a new species of Hipparchia from 

 the North-West Himalayas by Major G F. 1 . Marshall. — Notes 

 and drawings of the animals of various Indian land mollusca, by 

 Lieut. -Col. II. II. Godwin-Austin (PI. 5). — Some further results 

 of sun-thermometer observations, with reference to atmospheric 

 absorption and the supposed variation of solar heat, by H. F. 

 Blanford. 



The Archives des Sciences Physique et Naturelles for March 

 contains papers by M. Schneebeli, on the determination of the 

 absolute capacity of some condensers in electromagnetic mea- 

 surement ; by Raoul Gamier, on the great comet of September, 

 1882 ; by Dr. Julius Maurer, on the theory of the atmospheric 

 absorption of solar radiation. — M. Casimir de Candolle has an 

 interesting biographical notice of the eminent naturalist Emile 

 Plantamour. 



SOCIETIES AND ACADEMIES 

 London 



Royal Society, April 19. — " On the Limiting Thickness of 

 Liquid Film-." By A. W. Reinold, M.A., Professor of Physics 

 in the Royal Naval College, Greenwich, and A. W. Rucker, 

 M.A., Professor of Physics in the Yorkshire College, Leeds. 



The previous investigations of the authors have shown that 

 the specific electrical resistance of a soap film thicker than 

 374 x lo-'mm. is independent of the thickness, aid that the 

 composition of films formed of M. Plateau's " liquide glycerique " 

 may be largely altered by the absorption or evaporation of 

 aqueous vapour which attends even slight changes in the tem- 

 perature or hygrometric state of the air (Phil. Trans. Part II. 

 1881, p. 447)- 



In the present paper they describe a modified form of the 

 apparatus which they previously employed. The glass ca-e in 

 which the films are produced is surrounded by water, and addi- 

 tional precautions are adopted for maintaining the aqueous 

 vapour within it at the tension proper to the liquid of which the 

 films are formed. These changes have entailed considerable 

 alterations in details, but the main features of the apparatus 

 remain unaltered. The new form, however, possesses the im- 

 portant advantage that the temperature and hygrometric state of 

 the air in contact with the films can be kept perfectly constant 

 dining the progress of the experiments. With this apparatus a 

 number of measure- have been made of the electrical resistance 

 of films which have thinned sufficiently to show the black of the 

 fir.-t order of Newton's rings. To deduce the thickness from the 

 resistance, it is necessary to assume that the specific resistance 

 of the films is the same as that of the liquid in mass. The 

 authors' previous experiments do not enable them to assert the 

 truth of this assumption for such thin films, and it was therefore 

 important to ascertain by an independent method whether it 

 might be taken as approximately true. 



For this purpose between fifty and sixty plane films were 

 formed in a glass tube 400 mm. long and 18 mm. in inter- 

 nal diameter. The tube was closed by pieces of plate glass 

 and placed in the path of one of the interfering rays in a Jamin's 



"interferential refractometer." When the films had become 

 black, a known number were broken by bringing an electro- 

 magnet near to the tube and thus moving some sewing needles 

 which had been inclosed along with the films. The mean thick- 

 ness of the films was deduced from the displacement of the 

 interference " fringes " caused by their rupture. 



Two liquids were observed, viz. M. Plateau's "liquide glyce- 

 rique," and a soap solution containing no glycerine. The fol- 

 lowing are the means of the various groups of observations : — 



Liquid. Method. Mean thickness in terms 



or ro-G mm. 



"Liquide glycerique " ... Electrical 11 9 



Optical 107 



Soap solution Electrical 117 



Optical 121 



The agreement between these numbers is sufficiently close to 

 make the fact that they are approximately correct unquestion- 

 able, and to prove that the mean thickness of a black film is 

 nearly the same for both liquids. 



The electrical observations afford a means of comparing the 

 thick neses of different black films and observing whether or not 

 the thickness of the black portion of any particular film alters 

 as its area increases. The results obtained in the paper and in 

 a previous preliminary investigation on the same subject (Proc. 

 Roy. Soc., 1S77, No. 182, p. 334) are summed up by the authors 

 as follow s : — 



(1.) Persistent soap films which thin sufficiently to exhibit the 

 black of the first order of Newton's rin^s invariably display an 

 apparent discontinuity in their thickness at the boundary of the 

 black and coloured portions. 



(2.) The whole of the black region, at the time of or very soon 

 after its formation, is of uniform thickness. 



(3.) This thickness remains unaltered in any film, whether the 

 coloured parts of the film are thinning or thickening, increasing 

 (it- diminishing in extent. 



(4.) It is different for different films, but no connection has 

 been traced between its magnitude and the time which elapses 

 between the first formation of the film and the first appearance 

 of the black, or between either of these and the time of obser- 

 vation. 



(5.) The mean values of this thickness are the same to within 

 a fraction of a millionth of a millimetre, whether the films are 

 plane or cylindrical, in contact with metal or with glass, formed 

 of soap solut ion alone, or with the addition of more than two- 

 fifths of its volume of glycerine. 



(6.) Two tutally independent methods of measuring the thick- 

 ness rjf the black portions of the films give completely concordant 

 results. 



(7.) The mean value of the thickness calculated by giving 

 equal weight to the re-ults of the electrical and optical experi- 

 ments is 1 1 6 X 10- 6 mm. The extreme values formed were 

 7-2 X ic-" and 14-5 X 10- 6 mm. 



The smaller of these quantities is therefore a limiting thickness 

 to which a soap film in air saturated with the vapour of the 

 liquid from which it is formed rarely attains, and below which 

 none of the films observed by us have thinned. 



Linnean Society, May 24. — Anniversary Meeting. — Sir 

 John Lubbock, Bart., president, in the chair. — Mr. R. McLach- 

 lan read for the Audit Committee the statement of receipts and 

 payments for the year ; 750/. had been invested, and a balance 

 at banker's (April 30) remained of 514/. &s. yd. — The Secretary 

 (Mr. B. I). Jackson) read his annual Report. Since the last 

 anniversary 11 Fellows aid I foreign member had died and 11 

 withdrawn, while 54 new Fellows had been elected. Between 

 purchase, exchange, and donations, 407 volumes and 442 sepa- 

 rate parts had been added to the library. — Mr. G. J. Romanes, 

 on behalf of the subscribers, formally handed over the portrait of 

 Charles Darwin, painted by Mr. J. Collier, its exhibition at the 

 Royal Academy last year having then prevented its presentation. 

 — A bust of the late Prof. Louis Agassiz by the American 

 sculptor, Mr. Hiram Power, was handed over by Prof. Allman 

 to the Society as a present from the sculptor's son, Mr. H. 

 Power of Florence. — An engraving from Gainsborough's painting 

 of the old English naturalist, Mr. Thomas Pennant, w as presented 

 by Mr. Howard Saunder- in the name of Mrs. Alston, as a bequest 

 from her son, the Society's late secretary, Mr. E. R. Alston. — 

 The President then delivered his anniversary address, comment- 

 ing generally on the events of the past year, with special 

 reference to their bearing upon the Society ; in congratulating 



