144 Ana/i/sis of Scientific Books. 



without giving the author the trouble of new composition. The 

 same matter is reprinted in the second volume. 



The third chapter treats of simple combustibles. Of these, 

 his first genus contains " bodies forming acids, by uniting with 

 the supporters of combustion, or with hydrogen." We meet 

 here with nine substances, among which are silicon, arsenic, 

 and tellurium ; but he excludes chromium and tungsten, though 

 one might imagine they had rather a better claim than silicon, 

 to be regarded as acidijiable combustibles. " The present me- 

 thod," says he, " of confounding every thing under the name of 

 metal, has introduced much confusion into the science." We 

 know of no chemical writer, who has introduced such confusion 

 as Dr. Thomson, who has clashed together, silicon, sulphur, 

 arsenic, tellurium, and osmium, in one group. 



Under carbon, the only novelty is hydrocarbonic oxide, which 

 Dr. Thomson has ventured to embody in a system of che- 

 mistry, as, we fear, upon insufficient grounds ; for more than 

 one-third of the weight of ferro-chyazic acid is, by his own 

 account, azote ; yet when he decomposes that acid in the ferro- 

 chyazate of potash, by sulphuric acid and heat, he gets a gas 

 absolutely destitute of azote. 



In treating of chloric ether, he says, " I examined this com- 

 pound in 1810, and ascertained that it is a compound of defiant 

 gas and chlorine." He refers to the first volume of the Wer- 

 nerian Memoirs, p. 516. On looking over this paper on olefiant 

 gas, we find the only thing said about chloric ether, to be, 

 " It is a substance, of a nature quite peculiar, and seems to 

 consist of the two gases simply combined together." This is, 

 obviously, a mere guess, for he offers no analysis of it, yet 

 assumes the credit of determining its nature, after the researches 

 of M. M. Colin and Robiquet had developed it. In that paper, 

 we find him using, for another analysis, an olefiant gas, which, 

 by his own account, " contained 16 per cent, of common air, and 

 the oxygen gas was mixed with 1 1 per cent, of common air." 

 We should like to know how he ascertained so precisely, the 

 proportion of common air, when he was in the habit of operating 

 with such impure materials. 



In a note at the end of carbon, the Doctor says, " Mr. Brande, 

 in a paper just read to the Royal Society, has advanced the opi- 

 nion, that this gas (carburetted hydrogen) is only a mixture of 

 olefiant gas and hydrogen gas. But the specific gravity of the 

 gas is quite inconsistent with such an opinion. A mixture of one 

 volume olefiant gas and two volumes hydrogen, would possess 

 the chemical properties of carburetted hydrogen. But the spe- 

 cific gravity of such a mixture, instead of 0.555, would be only 

 0.36987." On the preceding page, we find the properties of 

 carburetted hydrogen to be such, that " for complete combus- 



