Jan. 13, 1887] 



NA TURE 



26- 



low pressures, where volume is large, the term a approaches and 

 finally equals zero, while b diminishes and finally becomes equal 

 to the value of c, calculated from the ordinary equation, 

 cT 

 /> = -■ 



V 



We have as yet only had time to apply this formula with ethyl 

 ether to the liquid state ; and as we are not yet quite certain 

 whether the relation holds for volumes between 4 and 20 c.c. of 

 I gramme of ether, we are at present engaged in measurements 

 of volumes and pressures at temperatures between 220° and 280°. 

 Assuming the above relation to be true (and it is at all events a 

 close approximation to truth), it is possible to calculate those 

 portions of isolhermals included within the liquid-gas area, and 

 represented in Andrew's diagram by horizontal straight lines. 

 We have calculated a few of these isothermals for ether, and 

 find that the areas above and below the horizontal lines (see 

 woodcut) are equal, when measured by a planimeter. 



Reserving a full discussion of the subject until the completion 



of our experiments, we would here point out the similarity 



between the equation p = bt - a and those proposed by Clausius 



and by van der Waals to represent these relations. Clausius's 



RT c 



formula is / = , 



v-a. T(r' + fl)'i 

 RT a 



and van der Waals' / = . 



v-b z^- 



In these formula; Clausius's a and c are equivalent to van der 

 Waals' b and a respectively, but R has a different signification. 



We find that a somewhat similar formula agrees better with 

 experiment than either of the above ; it is 

 RT a 



v-b Tv" 

 where R, /', and a have the same meaning as in van der Waals' 

 formula. This formula expresses the results of experiments with 

 great accuracy, where the volume of I gramme of ether occupies 

 not less than 25 c.c. ; but at smaller volumes it ceases to repre- 

 sent the facts. 



It is to be noticed that both Clausius's equation and ours 

 introduce T into the denoaiinator of the second term ; they 

 evidently differ from our first equation p = b/ - ti, in which a is 

 independent of temperature. 



We shall soon be in a position to communicate the results of, 

 this investigation, giving full data. 



Taris 

 Academy of Sciences, January 3. — M. Gosselin, in the 

 chair. — A new method of determining the constant of aber- 

 ration, by INI Loewy. M. Nyren having shown that none of 

 the methods hitherto adopted are free from systematic error, the 

 author here proposes a process by which all instrumental errors 

 may be avoided. It also eliminates the effects of precession and 

 nutation, and enables the observer to take accurate account of 

 the proper movements of the stars without depending on their 

 approximate values drawn from the catalogues. Lastly, it neu- 

 tralises the parallactic effect of the stars, dispensing with the 

 numerous experiments needed to determine the instrumental 

 constants. In a word, it calculates directly the phenomenon of 

 aberration itself, without employing any physical constant. — On 

 the relations of the lactiferous vessels with the fibro-vascular 

 system, and on M. J. Vesque's aquiferous apparatus of Calo- 

 phylluni, by M. A. Trecul. Further researches are described 

 confirming the conclusion already announced by the author 

 regarding the numerous points of contact between the milk- 

 yielding vessels and the various elements of the fibro-vascular 

 system in a large number of plants. It is further shown that 

 the anatomical results described by him in the year 1865 are 

 amply confirmed by M. Vesque's recent note on the aquiferous 

 apparatus of Calophyllum Calaba. — Actinometric observations 

 made during the year 1S86 at the Montpellier Observatory, by 

 M. A. Crova. 'The comparative study of these obser\'ations 

 (made by M. Houdaille with the author's actinometer) with those 

 of the three previous years confirms the conclusions already 

 arrived at regarding the annual variations of calorific inten- 

 sity in the solar rays. — Note on the diurnal nutation of the 

 terrestrial globe, by M. Folic. The important consequences of 

 the exi-.tence of this phenomenon for geology, astronomy, and 



geodetics are pointed out, and it is shown that it places beyond 

 doubt the fluid state of the interior of the globe surrounded by a 

 relatively thin outer crust. — Note on the Maclaurin series in the 

 case of a real variable, by M. O. Callandreau. — On a class of 

 difierential equations, by M. Emile Picard. — Observations rela- • 

 tive to M. P. Serret's recent note on a geometrical theorem, by 

 M. L. Lindelbff A slight error is pointed out in M. Serret's 

 calculation establishing the correspondence between the lines of 

 curvature in two surfaces with reciprocal vector rays. — Note on 

 the problem of electric distribution, by M. H. Poincare. The 

 author points out the defective character of the method prop 3sed 

 by MM. Neumann, Schwarz, and Harnack for solving this diffi- 

 cult problem. — Remarks resjjecting M. Hirn's observations on 

 the flow of gases, by M. Hugoniot. The author returns with 

 regret to this subject, and makes some final remarks on M. 

 Hirn's paradoxical inferences, calling upon him to present a 

 complete statement of his experiments, and of the causes of the 

 errors he professes to have detected in the calculations of the 

 upholders of the kinetic theory. — Note on the specific heats of a 

 perfect gas, by M. Felix Lucas. On theoretic grounds it is 

 argued tfiat the two specific heats of a perfect gas become in- 

 creasing functions of the temperature. — On the nature of the 

 electric actions in an insulating medium (second communication) 

 by M. A. Vaschy. These problems of electro-statics are 

 brought into general relation with those dealing with the 

 equilibrium of the ether regarded as an elastic body. It is hence 

 inferred that the electric perturbations must be propagated with 

 a uniform velocity, just as a mechanical concussion is pro- 

 pagated in an isotropic body, and this vijlocity must be that of 

 light. — On electric pressure and on electro-capillary phenomena, 

 by M. P. Duhem. — On a phosphate of hydrated silica, by 

 MM. P. Hautefeuille and J. Margottet. From three analyses 

 made with specimens obtained from different preparations it is 

 shown that the fonnula of this substance is Si02,2Ph05,4HO. — 

 Action of sulphur on ammonia and on some metallic bases in the 

 presence of water, by M. J. B. Senderens. These researches 

 have been carried out in continuation of MM. Senderens and 

 Filhol's studies in connection with the action of sulphur on the 

 saline solutions and on those of soda and potassa. — Note on the 

 maxima vapour tensions of acetate of soda, by M. H. I^escceur. 

 M. Berthelot's conclusion that there is no isomery either between 

 the solid salts or between the diluted solutions of the various 

 acetates of soda, are fully confirmed by the results here obtained 

 by a different process. — On the preparation of the isobutylamines, 

 by M. H. Malbot. It is shown that the three isobutylamines are 

 formed in proportions differing little from each other,the operation 

 constituting an effective method of preparing all these amines 

 simultaneously. — Isomery of the camphols and camphors, by 

 M. Alb, Haller. Here the author deals with the camphols of 

 madder, of Borneo {Dryobalanops campJiora), and of yellow 

 amber. — Heat of formation of some alcoholates of potassa, by 

 M. de Forcrand. Determinations are given for the heat of for- 

 mation of the propylate .and isobutylate of potassa. — On 

 some points relating to the action of saliva on the grain 

 of starch, by M. Em. Bourquelot. — Experimental researches 

 on mercurial intoxication, by M. Maurice Letulle. The 

 paper deals especially with the paralytic accidents and lesions 

 of the surface nerves caused by this intoxication (chronic 

 hydrargyrism;. — Studies of the relations existing between the 

 cranial nerves and the cephalic sympathetic nerve in birds, by 

 M. L. Magnein. — Note on the red and white muscles in the 

 rodents, by M. L. Ranvier. — Observations relative to M, 

 Maupas' recent note on the multiplication of Leucophrys pa/ii/a, 

 by M. Balbiani. It is shown that the peculiar process of 

 fissiparity in these organisms is not such a rare phenomenon as 

 is supposed by M. Maupas. — On the line of development 

 followed by the embryo of bony fishes, by M. L. F. Henneguy. 

 The author's researches confirm the conclusions already arrived 

 at by Kupffer and Oillacher. — On the amphipod crustaceans of 

 the west coast of Brittany, by M. Edouard Chevreux. — Obser- 

 vations relative to M. Viguier's note on the so-called ophite 

 rocks of the Corbieres, and to M. Deperet's communication on 

 the Devonian system of the Eastern Pyrenees, by M. A. F. 

 Nogues. — Microscopic examination of the ashes ejected by the 

 Krakata'b volcano, by M. .Stanislas Meunier. — A critical exami- 

 nation of certain rare minerals, by M. A. Lacroix. Descriptions 

 are given of pterolite, villarsite, griingesite, and gamsigradite. — 

 The death was announced of M. Francisque Fontannes, a dis- 

 tinguished geologist, who was awarded the Academy's Grand 

 Prize for the Physical Sciences in 1S83. 



