Academy of Sciences in Paris. 377 



and immediately afterwards, was still more increased by the feast of 

 Mina, at which every Mussulman kills a sheep, the blood and 

 entrails of which are left to rot on the public ways : thirty thousand 

 of these animals were killed in one day, and the putrefaction result- 

 ing increased to such a degree the intensity of infection, that Mina 

 was covered with corpses like a field of battle. The governor, 

 Abdenbeg, who would not neglect his religious duties, went to Mina 

 to assist in the sacrifice of sheep, and being attacked with the disease 

 in the night, had ceased to exist before the morning. Annexed to 

 this letter is the proces verbal of the post mortem examination of two 

 of the corpses by European surgeons at Mecca ; the symptoms are 

 similar to those observed in cases of cholera elsewhere. Tliis 

 interesting communication was referred to the Cholera Morbus 

 Committee. 



NATURAL PHILOSOPHY. 



Polarized Light. On the llth July M. Babinet communicated 

 the result of some experiments which he had made relative to the 

 unequal absorption of the two polarized rays of the coloured crystals 

 which have a double refraction. He states that * all the negative 

 crystals, such "as coloured spath, arragonite, tourmaline, &c., allow 

 the ray, which undergoes the extraordinary refraction, to pass in 

 excess. All the positive crystals, on the contrary, such as smoky 

 quartz, the gypsum of Montmartre, &c., transmit the ordinary 

 ray in great abundance. 



Vibration of Sound. On the 18th July M. Savart communicated 

 the result of his experiments made with an instrument, invented by 

 himself, for the purpose of ascertaining the greatest and least num- 

 ber of vibrations per second of which a sound may be composed so 

 as to be perceptible to the human ear. He had previously ascer- 

 tained that, in one extreme, sounds resulting from more than 40,000 

 simple oscillations per second, may be distinctly perceived ; and he 

 now stated, that, in the other, sounds may be produced by his ma- 

 chine, whicn are not only perceptible, but even intense, although 

 composed of but eight vibrations per second. The lowest limit of 

 perceptible sounds produced without the aid of his machine was 

 thirty-two vibrations per second. 



Conduction of Sound by Water. On the 8th of August, a letter 

 was read from M. Cagnard Latour, communicating an experiment 

 which he had made with the instrument called the %ren. It is well 

 known, that if the instrument be set in motion by a column of water 

 of sufficient elevation, a sound resulting from the vibrations of the 

 liquid itself is produced, even when the instrument is completely 

 submerged. M. Latour ascertained, that by plunging himself into 

 the water, and putting the syren in motion by injecting the liquid by 



2 C 2 



