240 Notes and Memoranda. 



NOTES AND MEMOBANDA. 



The Flowing- op Ice and other Solids under great Pressure. — M. 

 Tresca made a second communication to the Academy of Sciences of Paris at a 

 recent sitting, on this very interesting subject. An account of his first paper was 

 giyen in our Vol. vi., p. 464. He uses a strong cylinder, almost six inches in 

 diameter, and having at its lower end an aperture about two inches in diameter. 

 The more nearly the diameter of the opening approaches that of the cylinder in 

 size, the less the pressure which will be required. To render perceptible the 

 modifications which the bounding surfaces of the different portions of the ice 

 would undergo during their passage through the cylinder and aperture, portions 

 of it were either coloured throughout their masses, or on those faces which con- 

 stituted the joints. It was found that the ice comported itself in exactly the same 

 way as lead and ceramic pastes had done in the previous experiments, which we 

 have already described. But while a pressure of about 1792 lbs. per square inch, 

 or that of a column of water about 4000 feet high, was sufficient to cause the 

 flowing of the ice, lead had for the same purpose required a pressure of about 

 9000 lbs., or that of a column of water nearly 20,000 feet high. The effects 

 produced were very remarkable. The surfaces of the joints, originally plain, 

 were changed into concentric tubes, and the ice as it issued from the aperture in 

 the cylinder was furrowed by transverse fissures, so as to resemble a series of 

 discs rather than a continuous solid. This peculiarity had been observed also 

 with the less flexible porcelain pastes. It was apparently dependent on the nature 

 of the material used, and was evidently a secondary phenomenon, which took 

 place after the flowing had happened, and while the ice was actually within the 

 aperture of the cylinder, being due to the cessation of pressure. Each disc con- 

 sisted of many concentric layers, which must have been produced before the 

 separation into discs occurred. These experiments were believed to throw consi- 

 derable light on the theory of the movement of glaciers. Superimposed layers 

 were displaced, surfaces were distorted, layers were curved at the extremities of 

 the partial tubes, fissures were produced when pressure ceased, etc., just as in the 

 case of the glaciers. It was remarked that although the ice lost its original form, 

 it did not lose its transparency under the influence of pressure. 



Dissociation op Sulphurous Acid. — M. H. Deville, as explained in an 

 article, Yol. hi., p. 191, to which the reader is. referred for a description of the 

 apparatus, applies this term to the separation of the constituents of a compound, 

 at a temperature lower than that which would cause complete decomposition. 

 Sulphurous acid transmitted between the tubes he employs, the outer one being 

 at 2192° Fahr., and the inner, which was of plated copper, about 50° Fahr., 

 was decomposed, sulphur being deposited on the silver, but not combining with 

 it ; and sulphuric acid being formed with the oxygen, liberated and undecom- 

 posed sulphurous acid. 



Agp. at which the Moon can be Seen. — A subscriber at Runcorn remarks 

 on this subject that he saw the moon on the 8th of February, 1864, when it was 

 little more than 23 hours old. On another occasion he saw it when 43 hours 

 40 minutes old, and persons to whom he pointed it out said it was the narrowest 

 moon they had ever seen. It is obvious that the early visibility of our satellite 

 will depend upon her latitude at the time, and upon the state of the atmosphere. 

 Mr. Webb obligingly informs us that " Hevelius never saw the moon earlier 

 than 40 hours after conjunction with the sun ; and Schrbter's nearest points were 

 about 28o hours on either side. Beer and Madler saw it 18h. before conjunc- 

 tion, 1834, October 1, when the moon was 11° distant from the sun, and almost 

 vertically over it, 8° 36' above the horizon." Jews and Mahomedans are likely 

 upon religious grounds to watch for the earliest appearance of a new moon, and it 

 would be interesting to know what their experience has been. 



Action op Venus on the Sun. — In the Intellectual Observer, Vol. v., 

 p. 448, we published a very important paper, by Mr. Balfour Stewart, " On the 

 Origin of the Light of the Sun and Stars," and since that date we have men- 

 tioned the further researches of that careful observer. We now find in the Fro- 



