462 Intelligence and Miscellaneous Articles, 



Hill and Cold Comfort, and of the Gryphite and THgonia-be&s of 

 the neighbourhood of Cheltenham. The Gloucestershire Cepha- 

 lopoda-bed he regards as situated close to the bottom of the Inferior 

 Oolite series ; and this is also the position to which he refers the 

 sandy beds above-mentioned. 



4. " Cetarthrosaurus WalJceri (Seeley), an Ichthyosaurian from the 

 Cambridge Upper Greensand." By H. G. Seeley, Esq., E.L.S., E.G.S. 



In this paper the author described a small Ichthyosaurian femur, 

 discovered by Mr. J. F. Walker in the Upper Greensand of Cam- 

 bridge. He noticed the general characteristics of the femur in 

 Ichthyosaurians, and pointed out, as the chief peculiarities of the 

 bone that he was describing, the subovate form of its head, and the 

 presence of large flattened lateral trochanters* which, if of equal 

 dimensions on both sides of the bone, would have made its greatest 

 transverse measurement greater than its length. Upon this bone 

 he proposed to found a new genus, Cetarthrosaurus. 



LIX. Intelligence and Miscellaneous Articles. 



SOME EXPERIMENTS ON THE EFFECTS OF MAGNETISM ON THE 

 ELECTRIC DISCHARGE THROUGH A RAREFIED GAS WHEN IT 

 TAKES PLACE IN THE PROLONGATION OF THE AXIS OF THE 

 MAGNET. BYMM. ATJGTJSTE DE LA RIVE AND ^DOUARD SARASIN*. 



TINT the first memoir t which we published on the action of niagne- 

 ■■- tism on gases passed through by the electric discharge, we studied 

 first the case of the magnet acting upon a discharge perpendicular 

 to its axis. "We recognized that in this case the magnet, between 

 the two poles of which the Geissler tube is placed, has for its effect, 

 besides the deviation of the luminous jet, its condensation, and its 

 more intense brilliancy, a notable diminution of the elastic force of 

 the gas in the portion of the discharge which is more directly sub- 

 mitted to its action. This augmentation of density (produced, at 

 the expense of the rest of the gaseous mass, at the same time as the 

 condensation of the luminous jet) varies with the nature of the gas : 

 it is less strong with hydrogen than with carbonic acid, more feeble 

 with the latter than with air ; that is to say, the effect is the more 

 marked the less the gas is a good conductor of electricity. Besides, 

 this effect is more considerable on the portion of the discharge near 

 the negative electrode than upon the rest of the gaseous column 

 passed through by the current. As to the diminution of conducti- 

 vity of the gas which is known to result in this case from the 

 action of the magnet, we ascertained that it varies also very notably 



* This note, written shortly before the death of Auguste de la Rive for 

 the Jubelband of Poggendorff's Annalen, contains a resume of the last ex- 

 perimental researches to which the illustrious savant was able to devote 

 himself whose loss has been so grievously felt by Geneva and the entire 

 scientific world. — Editor of the Archives des Sciences. 



t Archives des Sciences Physiques et Naturelles, 1871, tome xli. p. 5; 

 Phil. Mag., Sept. 1871, vol. xlii. p. 211. 



