304 Intelligence and Miscellaneous Articles. 



not think that at the ordinary pressure a gas could completely fill a 

 vessel with 20,000 times the original volume of the gas. The sub- 

 stance of comets is therefore a kind of very divided matter, with its 

 molecules isolated and destitute of mutual elastic reaction. 



It follows from the preceding that both the mass and the density 

 of a comet are infinitely small, and without an}'' hypothesis we may 

 say that a sheet of common air of 1 millimeti-e in thickness, if trans- 

 ported into the region of a comet and illuminated by the sun, would 

 be far more brilliant than the comet. 



The mass of the earth, according to the average density given by 

 Baily, may be reckoned at 



6,000,000,000,000,000,000,000,000 kilogrammes ; 

 the matter of comets being assimilated above to air of which the 

 density would be 



45 ,000,000,000,000,000 

 times less than that of the ordinary air, this would lead us to assi- 

 milate it to the substance of the earth diminished to about 



194,000,000.000,000,000,000,000 

 times less than its ordinary density. By this estimate a comet as 

 large as the earth would only weigh 30,000 kilogrammes ; this makes 

 thirty tons of 1000 kilogrammes, or the weight of thirty cubic metres 

 of water. — Comptes Rendus, February 23, 1857, p. 357. 



ON AN APPARATUS TO DETERMINE THE SOLUBILITY OF SALTS AT 

 HIGH TEMPERATURES. BY CHEV. CH. VON HAUER*. 



Chev. Ch. von Hauer has invented an apparatus to determine 

 exactly the solubility of salts at high temperatures, an operation of 

 great difficulty and precarious exactitude under ordinary circum- 

 stances. Ch. von Hauer's apparatus (made by M, S. Markus), called 

 by him " thermo-lysimfetre," consists essentially of a strong vertical 

 cylinder of copper, with a solid bottom, and a cover to be screwed 

 on to the cylinder. In the side of the cylinder is an aperture closed 

 by a cylindrical piece of metal, so that this may be turned without 

 admitting the passage of air. This piece of metal supports in the 

 interior of the cylinder a ring, into which may be inserted a small 

 vessel of determined capacity, the opening of which is turned towards 

 the bottom of the cylinder. A sufficient quantity of the salt, of 

 which the solubility is to be found, is placed on the bottom ; the 

 cylinder is then filled with the dissolving liquid, screwed up so as to 

 exclude the air, and heated to the required temperature. By turning 

 the external cylindrical piece of metal, the ring and the small vessel 

 supported by it are brought upwards, and by a special piece of 

 mechanism the vessel is at the same time shut. When the whole is 

 sufficiently refrigerated, the small vessel is taken out of the cylinder, 

 and as its capacity is known, the proportion of salt dissolved by the . 

 liquid contained in it may be easily determined. This apparatus 

 may be used with security even for temperatures far above 100° 

 Centigrade. — Proc. Imp. Geol. Instit. Vienna, Feb. 19, 1856. 

 * Favoured by Count Marschall. 



