430 



NATURE 



[March 3, 1892 



pended. If an electrolyte be added to a liquid containing such 

 particles in a state of pedetic motion, the movement is soon 

 arrested, owing to the particles touching one another, and co- 

 hering to form clots or clusters. If no electrolyte be present, 

 the particles do not tend to touch each other. From micro- 

 scopic observations, it is calculated that a particle with a mass 

 of 2'8 X io~'- grams moves through, approximately, its own 

 diameter, 1-4 x 10"* cm., in a second. Such a particle has 

 one hundred billion times the estimated mass of a water mole- 

 cule ; hence, if its pedetic motion be produced by bombardment 

 from water molecules, these must exist in complex groups of 

 considerable mass and some stability. The fact that pedesis is 

 stopped by the addition of an electrolyte would appear to in- 

 dicate that the water complices are disintegrated in the presence 

 of ions. The effect of pedetic motion in a liquid is to cause 

 hydrostatic pressure ; such hydrostatic pressure would be less 

 on a membrane capable of penetration by the molecular aggre- 

 gates or particles than on one not so permeable. It is not 

 unlikely that these particles obey gaseous laws in regard to 

 pressure on the sides of the containing vessel, as microscopic 

 observations show that the relative velocity of the particles 

 depends on their mass and density. L. Meyer has pointed out 

 the great discrepancies existing between measurements of the 

 osmotic pressures of solutions and the pressures calculated on 

 the assumption that the dissolved substances obey gaseous laws. 

 These discrepancies may be best explained by considering that 

 combination of the dissolved substance with the membrane walls 

 takes place, and that, subsequently, dissociation of the compound 

 occurs at the other side of the cell wall, as in the case of hydro- 

 gen penetrating a palladium diaphragm. The author is dis- 

 posed to conclude that solution is merely subdivision and admix- 

 ture, accompanied by pedetic motion, that the true osmotic 

 pressure has never been measured, and that a continuous passage 

 can be traced between visible particles in suspension and matter 

 in solution. — The acid action of drawing-paper of different 

 makes, by W. N. Hartley. An examination of numerous 

 samples of the best drawing-papers shows that they all con- 

 tain free sulphuric acid. Water in which the paper has been 

 steeped yields a precipitate of barium sulphate, and solutions 

 of helianthin and azolitmin painted on to the paper give the 

 acid reaction. — The interactions occurring in flames : a cor- 

 respondence between Sir G. G. Stokes and H. E. Arm- 

 strong. Sir G. Stokes considers that the facility with which 

 steam is decomposed by glowing carbon favours the view that, 

 at a high temperature, oxygen coubines with carbon in preference 

 to hydrogen. He considers it necessary to distinguish carefully 

 between the changes which take place in the partial combustion 

 of a molecule and those which are produced in neighbouring 

 molecules as a result of the heat liberated. This latter change 

 may be termed a thermo-chemical one, in contradistinction to 

 a pure chemical change. In the blue base of a candle flame, 

 where oxygen is plentiful, pure chemical change may occur. 

 The blue part envelops for a little way the highly luminous 

 shell in which glowing carbon is present. This carbon may 

 owe its origin to a thermo-chemical change, the heat being 

 derived from the pure chemical change occurring just outside it. 

 The hydrocarbon spectrum may be due to a gas formed by a 

 pure chemical change ; this gas is generally supposed to be 

 acetylene, but Sir G, Stokes considers that it is more probably 

 methane. This unknown gas is a hydrocarbon, which, when 

 burnt in the pure state, would show but feebly, if at all, the 

 hydrocarbon spectrum. For, in order that it should show its 

 spectrum, its molecule must be in a state of violent agitation ; 

 this might be expected to be the case if it had just been formed 

 as the result of partial decomposition, but would not be so 

 merely because it was going to be destroyed by union with 

 oxygen. Dr. Armstrong, while admitting that the facts do not 

 justify the assertion that oxygen combines with hydrogen in 

 preference to carbon when a hydrocarbon is burnt with insuf- 

 ficient oxygen, is unprepared to adopt the view, advocated by 

 Sir G. Stokes and Prof. Smithells, that the' carbon is the more 

 combustible, and thinks that the actual condition of affairs is 

 far less simple than is expressed in the statement of either of 

 these views. There seems to be very little opportunity in 

 flames for simple heat changes to occur, the molecules of dif- 

 ferent kinds being so mixed up together. Thus opportunity is 

 given for interactions to occur, the end result of which is the 

 same as that of a simple heat change of the chief substance 

 concerned ; merely because a change occurring at one moment 

 is reversed the next, and so escapes notice. In this way, con- 



NO. II 66, VOL. 45] 



tiguous molecules may play the part of surfaces, and that there 

 can be little doubt that such actions are of primary impoitance 

 may be inferred from the well-known fact that the extent to 

 which the dissociation of water vapour takes place depends on 

 the character of the surface in contact with which it is heated, 

 and not solely on the temperature. In fine, it seems permis- 

 sible to doubt whether, under the conditions present in flames, 

 carbon is ever separated by simple heat changes. It will certainly 

 be unwise at present to infer that the oxidation of the hydro- 

 carbons, or the separation of carbon and also of hydrogen from 

 them, takes place entirely in any one way.— Properties of alco- 

 holic and other solutions of mercuric and other chlorides, by 

 S. Skinner. The author has determined the variation in the 

 boiling-point of alcohol produced by dissolving it in mercuric, 

 lithium, magnesium, and calcium chlorides, as well as the 

 variation in the boiling-point of a solution of hydrogen chloride 

 of constant boiling-point produced by mercuric chloride. He 

 has also studied the distribution of mercuric chloride between 

 the two solvents, water and ether. The results indicate that 

 mercuric chloride affords a case in which the measure of the 

 property is a simple function of the quantity of salt present, 

 whereas in the case of the other chlorides, the measure of the 

 property involves some higher power. — The isomeric a-bromo- 

 cinnamic acids, by S. Ruhemann. An account is given of 

 experiments on the action of ammonia and phenylhydrazine 

 on the a-bromocinnamic acids. 



Entomological Society, February 10.— Mr. Frederick 

 DuCane Godman, F.R.S., President, in the chair.— The 

 President nominated Lord Walsingham, F.R.S., Captain Henry 

 John Elwes, and Dr. D. Sharp, F.R.S., Vice-Presidents for 

 the session 1892-93.— Mr E. Meyrick exhibited a number of 

 %j^tc\m&xi%oi Euproctis fulviceps,^^\\i., taken by Mr. Barnard, 

 showing the extraordinary variation of this Tasmanian species, all 

 the males of which had been " sembled " by one female. The 

 males were represented by various forms ranging from black to 

 white, which had all been described as distinct species. Dr. 

 Sharp, Mr. Hampson, Mr. McLachlan, Colonel Swinhoe, Mr. 

 Elwes, Mr. Poulton, and Mr. Jacoby took part in the discussion 

 which ensued.— Dr. Sharp exhibited samples of pins which he 

 had tried for preventing verdigris, and stated that silver wire 

 was the best material to use, as insects on silver pins remained 

 intact, whilst those on gilt pins were destroyed by verdigris.— 

 Mr. G. T. Porritt exhibited a series of specimens representing 

 Huddersfield forms of Polia chi, including nearly melanic speci- 

 mens, found there during the last two seasons. He said these 

 forms had not hitherto been observed elsewhere.— Mr. Tutt 

 exhibited a series of Hadena pisi, comprising specimens very 

 grey in tint, others of an almost unicolorous red with but faint 

 markings, and others well marked with ochreous transverse 

 lines; three distinct forms of Hadena dissimilis ; red and 

 grey forms of Panolis piniperda, and a dark form of Eupithecia 

 fraxinata; also a specimen oi Sciaphila penziana.—The. Rev. 

 Dr. Walker exhibited specimens of Arge titea, A. lachesis, A. 

 psyche, A. theiis, and other species of the genus from the neigh- 

 bourhood of Athens ; also specimens of Argynnis phabe, taken 

 in Grenada in May 1891.— Mr. W. Farren exhibited a series of 

 specimens of Peronea variegana var. cirrana, and P. schal- 

 leriana var. laiifasciana, from Scarborough ; Eupacilia vecti- 

 sana, from Wicken Fen ; and Elachista subocellea, from Cam- 

 bridge.— Mr. G. A. J. Rothney sent for exhibition a number 

 of species of ants collected in Australia, in May and June 1886, 

 which had recently been named by Dr. Forel. The collection 

 included : Iridomyrmex pufpurens, Sm., /. rufomger, Lowne, 

 /. gracilis, Lowne, /. itinerans, Lowne, Ectatomma 7Jietalhctim, 

 Sm., E. nudatnm, E. mayri, Aphanogaster longiceps, Sm., 

 Polyrhachis amnion, Fab., Myrmecia nigriveiitrts, Mayr, and 

 nigrocincta, Sm. ; and a variety of Camponotus rtibigmosus, 

 Mayr, from Brisbane ; also a few species from Honolulu ; 

 and a species of Monomorium, which Dr. Forel had not 

 yet determined.— Mr. C. O. Waterhouse read a paper en- 

 titled " Some Observations on the Mouth Organs of Diptera, 

 which was illustrated by numerous diagrams.— Mr. E. Meyrick 

 read a paper entitled "On the Classification of the Geo- 

 metrina of the European Fauna." Mr. Hampson, Mr. Elwes, 

 Mr. McLachlan, Colonel Swinhoe, Mr. Tutt, and Mr. Distant 

 took part in the discussion which ensued. 



Zoological Society, February 16.— Osbert Salvin, F.R.S., 

 Vice-President, in the chair.— Mr. W. T. Blanford, F.R.S., 

 exhibited two heads and a skin of the Yarkand Stag, lent for 



