238 Royal Society. 



3^ inches. When the cock of the boiler was opened, the steam 

 struck on the lower side of the ball and passed thence to a wire- 

 gauze screen, placed at a distance of ten inches from the ball ; 

 this screen was connected with the two-leaved electrometer. 

 Positive electricity passed veiy slowly to the screen ; but on now 

 allowing the steam to escape negatively electrified, the leaves of 

 the electrometer almost immediately diverged to their full extent ; 

 on shutting off the steam, ])ositive electricity began to pass about 

 as slowly as before ; again allowing the steam to play on the ball, 

 the leaves diverged with positive electricity as previously, and 

 these actions could be repeated a great many times. 



181. The account of the jet of steam (62.), when the rough 

 noise is being produced, is not sufficiently full and accurate. 

 The main distinction in the appearance of the jet of steam with 

 the hiss and the roar is, that with the hiss there is a transparent 

 space between the orifice and the steam-cloud of about half an 

 inch ; but with the roar this intei*val is of a dense white ; and 

 the mass of white can be seen to extend two or three inches into 

 the steam-cloud, as it does not diverge from the axis of the pro- 

 jected jet so rapidly as the steam. AVhen there is only a smooth 

 hiss, one or more transparent lines of water proceed from the 

 edge of the orifice, and which I think are never longer than the 

 one-eighth of an inch, and certainly shorter if more than one 

 fibre appears. If when the roar is set up, the jet of steam be 

 viewed near to the orifice, the whiteness is seen not to be uni- 

 form, but to be made up of a number of little white cones, having 

 their vertices stuck on the margin, and I think also on the inte- 

 rior of the orifice, which cones coalesce at a short distance from 

 the orifice. The cones are apt to proceed from the same places 

 which the fibres of water frequent ; perhaps they are produced 

 from the fibres by a rotary motion resulting from two rectangular 

 vibrations. 



7 Prospect Place, Ball's Pond Road. 



XXXV. Proceedings of Learned Societies. 



ROYAL SOCIETY. 



[Continued from p. 158.] 

 May 8, 1851. — The Earl of Rosse, President, in the Chair. 



A PAPER was read, entitled " Memoir on the Megatherium. 

 Part II." By Prof. Owen, F.R.S. Received May 6, 1851. 

 The author premised a brief sketch of the successive steps which 

 had led to the knowledge of the Megatherium acquired at tiie date 

 of his researches, and of the different hypotheses which had been 

 broached of its affinities, habits and food. He then recounted the 

 mode of the acquisitionof theeomplete skeleton, and of its articulation, 

 at the British Museum, and commenced its description by the ver- 

 tebrae of the trunk. These consist of 7 cervical, 16 dorsal, 3 lumbar. 



