196 PROCEEDINGS OF THE SOCIETY OF 



a etroi)"- mnjnif'tic power. This action tends to augment the resistance of the 

 gascous'sul>.<tance to the transmission of electricity, hy condensing the gaseous 

 tihimi-nts, and has in particular the effect of rendering luminous the obscure 

 part of the column, by contracting the ])reviously too much dilat-'d gas which 

 occurs there. Lastly, the attention of i\I. de la Rive was especially drawn to 

 the rotatory and expansive action of magnetism on the electric discharge. IIo 

 has succeeded in obtaining, in regard to this point, certain very constant f icts, 

 such as those relative to the duration of the rotatory movement of the discharge, 

 which varies with the direction of the current, the nature of the gas, and its 

 degree of density, lie has also remarked the very great difference which the 

 phenomenon presents, according as the rarefied gas is dry or contains vapor 

 of water or of alcohol. In the lirst case, the luminous discharge expands undei- 

 the influence of magnetism into a sheet which forms the surface of a sector, or 

 even that of a full circle when the gas is very much rarefied. In the case in 

 which vapor is present in the rarefied gas, the discharge, instead of expanding, 

 divides into a greater or less number of small partial j(.'ts at equal interspaces, 

 forming, as it were, a star animated by a movement of rotation around its centre. 

 These ])henoTnena, and others of the same kind, have led M. de la Hive to 

 cstablisli a difference between permanent gases and vapors, in reference to the 

 point of cohesion, or rather their molecular constitution. The author termi- 

 nated the reading of his m'emoir with some general considerations on this exteu- 

 •givc subject ; announcing that, for the present, conclusions too absolute would 

 be ])remature, and that he abstains from presenting them until he shall have 

 completed his researches by extending them to a greater number of gaseous 

 eubslances.' 



If we have enlarged a little more than is usual in an analysis of the memoir 

 of M. de la Hive, wc find a justification, not only in the importance of the sub- 

 ject, but in the circumstance that the results which he obtained have been here- 

 tofore published only in fragments. The entire memoir is nbout to appear iu 

 the seventeenth volume of tlu; Memoirs of the Society, now in the jjress.* 



It should be added, that we owe to 51. de la Rive the model of a new system 

 of Grove's apparatus. The modification which he has introduced into llu; bat- 

 tery of that jiiiysicist is essentially calculated to render its managemcnit more 

 commodious and ju'ompt. Ilis instrument, which is extremely manageable, and 

 is furnished with conductors of alumina, jjossesses the advantage of reqiiiiiug 

 little; manipulation, and of rendering superfluous the removal of the nitric 

 acid ; the same acid suflices for the service of several days and many experi- 

 ments. AVith the help of a single pair of this battery, i\I. de la llive has been 

 able to repeat all tin; principal experiments of the electro-dynamics of Ampere — 

 experiment!? which usually require five or six pairs of Grove or of Bunsen. 



Besides some verbal communications by I*rofi;ssor Wartmann relative to 

 electrical phenomena, particularly to the limit of pressure which permits a 

 spark to pass through a gaseous medium, as well as to the influence which the 

 Btate of tension of a gaseous medium exercises on the passage of a current, the 

 eavant just named engngod the attention of the society by an account of some 

 of the principal subjects discussed iu the last reunion of the British Association 

 at Cambridge, at which he was present. Among the communications made on 

 that occasion, 31. Wartmann cites more particularly the observations of M. 

 Kasmilh relative to tin; structure of the sun. To avoid the inconvenience of a 

 too great light, ]\I. Nasmith, instead of introducing tin; solar rays dinctly into 

 the i-ye, "places near the oljject glass a lens which is plane on the side next the 

 eye, but concave on the opposite side, so as to disperse the luminous rays and 

 allow tin; study of only the quantity of light reflected by the plane surfice. 

 The author has thus been able to ascertain that towards the hour of noonday 



* A full t^llIl^l,•ltiou of tliis interesting nicuioh- h g-iveu iu this report. — Sec pajje 



