Notes and Memoranda. 159 



Heat eeoh Botation oe a Disc in Vacuo. — Mr. Balfour Stewart and Mr. 

 P. Gr. Tait have been for some time engaged in very curious and important ex- 

 periments on the heat acquired by the rotation of a disc of metal in vacuo. The 

 Proceedings of the Royal Society, Wo. 76, contains a paper on this subject, from 

 which it appears that a disc of aluminium, thirteen inches in diameter, was caused 

 to revolve rapidly in a vacuum chamber. After moving for about forty seconds, 

 at the rate of 2500 per second, a heating effect equal to 1° P. was indicated by a- 

 thermo-electric pile. The writers detail various reasons for believing that the 

 augmentation of heat did not arise from the friction of the bearings, nor to 

 "revolution under the earth's magnetic force," and they say that they are reduced 

 to two possible causes — the friction of the ah, which cannot be entirely got rid of 

 in any artificial vacuum, or " the "possibility that simple motion becomes dissi- 

 pated by an etherial medium in the same manner, and possibly to nearly the 

 same extent, as molecular motion, or that motion which constitutes heat," or the 

 effect may be partly due to air and ether. It could not be due to air, because, 

 in the first place, it was found not to be proportioned to the quantity of air left 

 in the vacuum. Professor Maxwell and Mr. Graham considered that the fluid 

 friction of air was not dependent upon its tension, and therefore diminishing the- 

 quantity of air in the vacuum would not proportionally diminish the friction 

 action. Hydrogen fluid friction is much less than that of atmospheric air, but 

 when a hydrogen vacuum was employed, the heating effect was so nearly the 

 same as in an air vacuum, as to offer a second reason for not ascribing the heat- 

 ing to this kind of action. 



New Mode oe Salting Meat. — M. Pienkowski informs the Academy of 

 Sciences (Paris), that acetate of soda leaves meat in a condition in which it may 

 be easily dried, has a pleasant smell, and can be unsalted easier than when pre- 

 pared with chloride of sodium. 



LTViNa Bodies and Lightning-. — In our last number we mentioned the 

 case of a flock of sheep and their shepherd being struck by lightning on the Ourthe. 

 M. A. Be la Bive, commenting on this incident in the Archives cles Sciences, 

 observes that an agglomeration of men or animals in the open air augments the 

 danger of their being struck by lightning, either by accumulating a greater mass 

 of conducting matter on one spot, or by giving rise to an ascending column of 

 vapour down which the lightning descends. Sheep, he says, herd very close 

 together when they are frightened, and would thus produce this effect in a striking 

 degree. He recommends persons caught in a storm not to stand too near each 

 other. 



Alleged Bemedt eoe Consumption. — Dr. Schnepp of Eaux-Bonnes states 

 in the Presse Scientifique that an excellent effect is produced in consumptive 

 patients by a fluid he calls galazyme, which bears some resemblance to the 

 Jcumis of the Tartars, to which they ascribe valuable qualities. He takes two parts 

 of asses' milk and one of cows' milk, and allows them to ferment. The fluid thus 

 obtained should be clear and sparkling. He gives one or two glasses a day for a 

 commencing dose, and raises the quantity to one or more bottles. 



The Colour oe Maes. — Monthly Notices contains a paper on Mars by the 

 Bev. W. B. Dawes. He concludes that the ruddy tint of this planet doe3 not 

 arise from any peculiarity of the colour of its atmosphere, as the redness is most 

 apparent in the centre where the atmosphere is thinnest. 



Mobility oe the Sun's Photospheee. — Mr. Brodie observed on 10th May, 

 1864, a large oval spot in the sun, and fringed all round with beautiful filaments 

 of luminous matter stretching over and towards the centre of the umbra. In the 

 course of three and a half or four hours, an unusually wide bridge of luminous 

 matter had formed completely across the spot ; . . . the bridge of luminous matter 

 was about 3500 miles wide, and being formed across the oval-shaped umbra, at 

 some little distance from its minor axis, the length might possibly not have been 

 more than 5500 miles at that point. This would give the- enormous velocity of 

 1400 miles per hour to the luminous matter which formed this bridge." — Monthly 

 Notices. 



