proceedings of the polytechnic association. 597 



Substitute for the Sand-Bath. 



Dr. Eloumcycr lias suggested a very useful contrivance for superseding 

 the inconvenient sand-bath in the distillation of liquids with high boiling 

 points, which consists in surrounding the retort with short fibres of asbes- 

 tos, which are held in place by wire gauze. 



The Age of the Pyramids. 



Mahmound Bey, astronomer to the Viceroy of Egypt, charged to investi- 

 gate the positions of the pyramids, has found that the lateral faces of the 

 great pyramid form with the horizon an angle of 51 degrees and 45 

 minutes, and that precisely the same angle of inclination is presented by 

 the lateral faces of the pyramids of Memphis. The uniformity of the pyra- 

 mids in this respect, and also in relation to the points of the compass, is of 

 itself indicative of their having been built with some reference to the stars; 

 and Mahmound Bey found that when the star Sirius crosses their meridians, 

 its rays fell almost perpendicularly upon the southern faces. This dis- 

 covery led him to calculate the date at Avhich, supposing the pyramids to 

 have been in existence, the rays of Sirius, at the moment of crossing the 

 respective meridians of their localities, would fall exactly perpendicular to 

 tfieir southern faces ; and the result of his calculations is, that this would 

 be about 3,300 years b. c. According to the principles of astrology, the 

 influence of a star is greatest when its rays fall perpendicularly upon 

 the object. The brightest of the stars — Sirius — was dedicated by the 

 Eg3'ptians to the god Sothis, whom they supposed to have all funeral 

 monuments under his, special protection. The view of Mahmound Bey 

 strikingly accords with Bunsen's calculation, that the builder, Cheops, 

 flourished in the thirty-fourth century before the Christian era. 



On the Cause of Rolling Thunder. 



M. Yionnois, in a note to the French Academy, explains the cause of 

 rolling thunder. He was at the camp at Nancy and heard the echo of the 

 firing, not sharp and dry, but somewhat confused and prolonged. He then 

 noticed that he was separated from the field by some trees, and concluded 

 that the leaves of those were the reflecting sui-faces. This led him to 

 think that the explosion of the electric spark might be reflected by the 

 vesicular vapor of the clouds, and the noise be softened and prolonged by 

 the inequality of the distances and the successive reflections. 



Cause of Rottenness of Cotton Cloth. 



Dr. Calvert read a communication to the London Chemical Society, "On 

 the Action of Silicate and Carbonate of Soda upon Cotton Fibre," contain- 

 ing his investigations into the cause of the rottenness apparent in some 

 white and blue-dyed cloths which were shipped to South America about 

 two years ago and returned to Manchester in consequence of their damaged 

 condition. He found the goods had not been finished by the old starch- 

 dressing, but had been treated according to the modern process, with a 

 solution of silicate of soda, and he then expressed the belief that an oxidi- 

 sing action had been set up. 



