Philosophical Transactions. 103 



which coincides, as nearly as can be expected, with the actual 

 specific gravity of the gas submitted to analysis, viz. .308. To 

 place the correctness of the results beyond question, our author 

 mingled the gases in tlie above proportions, and acted on the 

 artificial mixture in the same manner as on the original gas, when 

 he had the satisfaction to find that the analytical process again 

 gave the true volumes with the most perfect correctness for the 

 hydrogen and carbonic oxide, and within the fraction of a 

 measure for the carburetted hydrogen. Notwithstanding this 

 successful result, which was twice obtained, Dr. Henry observes 

 that he should still prefer, for the reason which has been stated, 

 having recourse to a temperature carefully regulated, for the 

 analysis of similar mixtures, in all cases where the hydrogen is 

 in moderate proportion, and where great accuracy is desirable. 

 Whenever (it may again be remarked) olefiant gas is present in 

 a mixture, it should always be removed by chlorine, before 

 proceeding to expose the mixture to the agency of the spongy 

 metal. 



It can scarcely be necessary to enter into further details re- 

 specting methods of analysis, the application of which to parti- 

 cular cases must be sufficiently obvious, from the experiments 

 which have been described on artificial mixtures. The apparatus 

 required is extremely simple, consisting, when the balls are em- 

 ployed, of graduated tubes of a diameter between 0.3 and 0.6 of 

 an inch ; or, when an increased temperature is used, of tubes 

 bent into the shape of retorts, of a diameter varying with the 

 quantity of gas to be submitted to experiment, which may be 

 from half a cubic inch to a cubic inch or more. These, when in 

 use, may be immersed in a small iron cistern containing mercury, 

 and provided with a cover in which are two holes, one for the 

 tube, and the other for the stem of a thermometer, the degrees 

 of which are best engraved on the glass. 



*' By means of these improved modes of analysis,'* says our 

 author, *'Ihave already obtained some interesting illustrations 

 of the nature of the gases from coal and from oil. I reserve, 

 however, the communication of them, till I have had an opportu- 

 nity of pursuing the inquiry to a greater extent, and especially 

 of satisfying myself respecting the exact nature of the compound 

 of charcoal and hydrogen, discovered some years ago by Mr. 

 Dalton, in oil gas, and coal gas, which agrees with olefiant gas 

 in being condensible by chlorine, but differs from it in affording 

 more carbonic acid and consuming more oxygen." 



We have anxiously looked for Dr. Henry's further remarks 

 upon the very interesting subject of this communication, more 

 especially as relating to the constitution of oil gas, connected 

 with which there are so many curious and anomalous circum- 

 stances, that we are convinced their thorough investigation would 



