March 5, 1885] 



NA TURE 



42; 



yeast, and on the phenomena of fermentation, by A. Certes and 

 D. Cochin. — On the presence of duodenal anchylostoma in some 

 Belgian hospitals, by Ch. Fisket. — On the presence of a coxal 

 gland in Galeodes araneoides, by J. MacLeod. — Note on G. 

 Edon's wurk on the Carmen Arvale, by Alph. Le Roy. — Some 

 details on Wissant and it-, identification with the Portia Iccius 

 of the Romans, by Alph. Wauter. — On the apparent enlarge- 

 ment of the orbs of the sun and moon, by Paul Stroobant. — On 

 a new Balenoptera rostra/a in the Mediterranean, by J. Van 

 Beneden. — Discourse on geological chronology, by Ed. Dupont. 

 — On the chief cause of cyclones and tropical calms, by M. Folie. 



Bulletin de !' Academic des Sciences de Si. Petersbourg, tome 

 xxix. No. 4. — On the applications of the interpolation method 

 . M \\ . I chebychef, by O. Backhand (in German). 

 The fine method of the Russian mathematician is shown to be 

 easily represented in a simple scheme, appropriate to calcula- 

 tions, and the author applies it to three examples, one of which 

 is the calculation of Ilasselberg's spectral observations. He 

 shows that, with regard to the easiness and simplicity of 

 calculations, the Tchebychef method leaves nothing to desire, 

 while its results are as reliable as those obtained by the much 

 more tedious method of least squares. Two other examples, 

 one for the declinations as taken from the Cape Catalogue, and 

 compared with those measured at Pulkova, and another for inter- 

 po'ating Pulkova double-star observations, give the same satis- 

 factory results. As known, Tchebychef's method permits also 

 to proceed without making any previous hypothesis as to the 

 degree of the interpolation formula. On the whole, when a 

 considerable number of data is given, and the least squares' 

 method becomes especially tedious, Tchebycheff' s method gives 

 excellent results. — The elements and the ephemerides of the 

 Encke comet for its appearance in 18S4-85, by O. Backlund. 

 The ephemerides are given from November 7, 1884, to May 6, 

 1885. — Demon-tration of several theorems relative to the nu- 

 merical function E(x), by V. Bouniakovsky (in French). — Con- 

 tributions to the Ornis of the Ternate Island, by Th. Pleske (in 

 German). The birds brought from the above' island by Dr. 

 Fischer are determined with thehelp of Salvadori's " Ornithologia 

 della Papuasia," &c. There are eighty-five species described. 

 — Remarks on the Etapomo-phus genus of Calamaride serpents, 

 by A. Strauch (in German) Having received an herpetologic 

 collection from Brazil, from Dr. Ihering, Prof. Strauch found in 

 it a new species of Elapomorphus, which he describes under the 

 name of E. lAeringii, and he accompanies the description by a 

 thorough critical revision of all known species of the same 

 genus. The paper is thus a systematic monograph of the genus, 

 which contains now eighteen species. 



The Belgique horticole for July to September, 1884, contains 

 a retranslation of Prof. Jacobsthal's essay on " The Evolution of 

 Vegetable Forms in Decorative Ait," an 1 M. Guirand's 0.1 the 

 gardens of the Mediterranean coast, which have already ap- 

 peared in our columns. We have also other a; tides of interest 

 taken from othrr journals, and the usual descriptions and admir- 

 able coloured plates of new plants. 



SOCIETIES AND ACADEMIES 

 London 



Royal Society, February 12. — " Note on the Condensation 

 at the Surface of (.lass.'' (Preliminary.) By J. T. 

 Bottomley, M.A , F.R.S.E. Communicated by Prof. Sir 

 William Thomson, F. U.S. 



It is well known to those who have endeavoured to obtain, in 

 glas- vessels, the very perfect vacuums first sought after and 

 obtained by Crookes, and producible by the mercurial pumps, 

 that the operation is much assisted by heating the glass vessels 

 to be exhausted, and even the tubes of the pump, to a high 

 temperature. The difficulty of removing the film of air and 

 moisture adhering to glass tubes is also well known to makers of 

 barometers and thermometers. 



When the Sprengel pump is used for producing a vacuum, 

 and when a tolerably good vacuum has been produced, so that 

 the barometric gauge indicates a 'presence of one millimetre or 

 half a millimetre of mercury, the dro,;s of mercury falling in the 

 tube of the Sprengel give rise to a loud metallic hammering 

 sound ; and they fall with such unbroken sharpness that those 

 who use this form of pump are often troubled by the "fall- 

 tubes " splitting longitudinally through a length of several inches 

 — a phenomenon in itself very remarkable, considering the 

 strength of the tubes and the smallness of the mercurial drops. 



If, while this hammering is going on, the glass vessel which is 

 being exhausted and the leading tubes of the Sprengel pump be 

 heated by passing the flame of a spirit-lamp or of a Bunsen 

 burner over them, the hammering immediately ceases, and on 

 looking closely at the fall-tubes it is seen that they are carrying 

 down air which the heat has liberated from the glass walls of 

 the apparatus. The ordinary barometer-gauge is scarcely sen- 

 sitive enough to show an increase of pressure, but the McLeod 

 gauge readily shows it. 



There is another w-ell-known phenomenon connected with the 

 condensation of gases and vapours on the surface of glass : viz. 

 the condensation of a watery film over the glass of electric 

 apparatus, in virtue of which, at temperatures considerably above 

 the dew point, the glass supports are not insulators of electricity. 

 This film of moisture is removed by exposing the glass stems to 

 heat, or to an artificially dried atmosphere. Some years ago, 

 at the wish of Sir William Thomson, I endeavoured to weigh 

 this film of moisture, but was absolutely unsuccessful. The 

 film must be of extreme tenuity. Prof. Quincke has, however, 

 made important researches on the "distance of capillary action " 

 and on some of the properties of these very thin films. His 

 results are given in two papers : Poggaidorff 's Annalen, toS, 

 p. 326, 1859; and Wiedemann's Annalen, vol. ii. 1877, p. 145. 

 He finds their thickness to be comparable with 5 X io -5 cm. 



With the view of measuring the quantity of gas condensed 

 upon a given surface of glass, I caused to be prepared in August 

 last a large quantity of fine glass thread. Some of this was of 

 flint glass rod or cane, which was softened in the blowpipe 

 flame, and drawn out on to a wheel. The remainder was of 

 flint glass tubes, drawn out in a similar way. The spun glass 

 was carefully parcelled up in paper and put aside till I should 

 be ready to use it. 



On January 3 I put a quantity of the non-tubular glass fibre 

 into a glass tube 2 cm. in diameter and 12 cm. long, and at- 

 tached it by a glass sealing to a five-fall Gimingham Sprengel 

 pump. The pump, which was in excellent order, was then 

 worked rapidly till I had produced a very good vacuum, which 

 by the McLeod gauge gave me an indication of o'3 M pressure. 1 

 The pump was then left for about an hour, and at the end of 

 that time, passing one more bottle full of mercury through the 

 pump, I ascertained that the vacuum had not sensibly deterior- 

 ated, the McLeod gauge giving identically the same reading as 

 before. This exhaustion was performed without the application 

 of any unusual heat to the tube containing the glass fibres. The 

 temperature of the room was about 56° F. 



I now raised the mercury to the upper level and allowed it to 

 flow through the pump, and the drops fell with the well-known 

 loud hammering noise. While this was going on I applied a 

 Bunsen burner to the tube containing the spun glass. In a few 

 seconds the hammering of the mercury ceased, and on applying 

 the test of the McLeod gauge the pressure within the pump was 

 found to have risen largely. I did not, however, obtain a mea- 

 surement with the gauge corresponding to the maximum pressure 

 of the gas driven off, or to any particular state. 



I now proceeded to pump out all the gas I could, working 

 the pump and heating the tube containing the glass fibres 

 strongly. The heating was carried on from time to time till the 

 tube, which was of German glass, showed signs of softening and 

 of falling in ; and the glass fibres were likewise, some of them, 

 slightly softened and bent. 



The pump was worked for over an hour, the heating being 

 applied, and the gas, which was easily seen being carried down, 

 was collected in a tube made for the purpose, which was fitted on 

 over the upturned ends of the five fall-tubes. At the end of this time 

 the vacuum was again fairly good, though not so good as it was 

 before the heating commenced. The McLeod gauge indicated 

 I '2 M- It was seen that very little more air was being carried 

 down, and I did not wish to push the vacuum farther than, or 

 quite so far as, the vacuum which had been obtained before the 

 liberation by heat of the condensed gas. 



The collecting tube was now removed, and the gas obtained 

 was measured and analysed, so far as it was possible to analyse 

 a quantity so small. 



The total amount of gas collected was calculated to be, at 

 15° C. and a pressure of 760 mm., C45 of a cubic centimetre. 

 To this a small quantity of strong solution of caustic potash was 

 added, and time was given for absorption. A small quantity of 

 pyrogallic acid was next added, and the further absorption 

 observed. The residue was so small that I could do nothing 

 farther. 



1 31 standing for one-millionth of an atmo. 



