Tloynl Society. 61 



The author, in this paper, has prosecuted more immediately and 

 more minutely than in his former communication*, the inquiry into the 

 structure of the ovary of the Ornithorhynchus, with a view to determine 

 its exact relations with that of the normal Mammalia, and of the ovi- 

 parous Vertebrata. He has obtained from this investigation the full 

 confirmation of the truth of the opinion he had previously formed, that 

 lactation might coexist with a mode of generation essentially similar 

 to that of the Viper and Salamander 3 and this fact has been further 

 established by the subsequent examination which he has made of the 

 uterine foetus of the Kangaroo. 



The author traces the regular gradation which obtains in different 

 orders of Mammalia in which true viviparous or placental generation 

 takes place, towards the ovo-viviparous or oviparous modes, in which 

 the exterior covering of the ovum never becomes vascular, and shows 

 that the Ornithorhynchus constitutes a connecting link in this chain. 



Drawings illustrative of the anatomical descriptions of the parts 

 examined hy the author accompany the paper. 



11." Observations with the Horizontal and Dipping Needles, made 

 during a Voyage from England to New South Wales." By James 

 Dunlop, Esq. (vommunicated by Capt. Beaufort, R.N., F.R.S. 



This paper contains a very numerous and uninterrupted series of 

 magnetical observations, made in the circumstances stated in the title, 

 and extending about 180 degrees in longitude and 100 degrees in 

 latitude. The apparatus, of which a detailed description is given, was 

 suspended from the roof of the cabin, and no alteration was made in 

 its suspension from the beginning to the end of the voyage. 



12. " Experiments on Light." By Henry Fox Talbot, Esq., M.P., 

 F.U.S. This paper will be found in our last Volume, p. 321. 



13. " On the Mummy Cloth of Egypt j with Observations on the 

 Manufactures of the Ancients." By James Thomson, Esq., F.R.S. 

 Communicated by Dr. Roget, Sec. R.S. This paper will also be 

 found in our last Volume, p. 355. 



14. " An Account of some Experiments to measure the Velocity of 

 Electricity, and the Duration of Electric Light." By Charles Wheat- 

 stone, Esq., Professor of Experimental Philosophy in King's College, 

 London. Communicated by Michael Faraday, Esq., F.R.S.f 



The continuance for a certain time of all luminous impressions on 

 the retina prevents our accurately ])erceiving, by direct observation, 

 the duration of the light which occasions these impressions , but by 

 giving the luminous body a rapid motion, which produces the appear- 

 ance of a continued train of light along the path it has described, its 

 condition at each moment may be ascertained, and consequently its 

 duration determined. The same law of our sensations precludes us 

 from direct perception of the velocity with which the luminous cause is 



* An abstract of Mr. Owen's former communication was given in Lond. 

 nnd Edinb. Phil. Mag., vol. i. p. 384. See also vol. ii. p. 71 ; vol. iii. pp. 62, 

 301 ; vol. iv. p. 54 ; and vol. v. pp. 145. 147, 235. 



f See Lond. and Edinb. Phil. Mag., vol. iii. pp. 81, 204; and vol. iv. 

 pp.113, 114. 



