hydrogen 1, as is the case with olefiant gas; but these are so com- 

 bined and condensed as to occupy only one half the volume they do 

 in that substance. A volume therefore of the gas contains four pro- 

 portionals of carbon 24, and four of hydrogen, 4 = 28, which is its 

 specific gravity. 



Beside the remarkable difference thus established between this 

 substance and olefiant gas, it is also distinguished by the action of 

 chlorine, which forms with it a fluid body, having a sweet taste, and 

 resembling hydrochloride of carbon, but from which a chloride of 

 carbon cannot be obtained by the further action of chloride and 

 light. 



The other products from the original fluid do not present any cha- 

 racters so definite -as the above substances; at the same time they 

 appear to be very constant, boiling uniformly at one temperature. 

 They cannot be separated by distillation into more and less volatile 

 parts, so as to afford means of reducing their number to two or three 

 particular bodies. They have the general properties of the original 

 fluid, and with the other products, are all peculiarly acted upon by 

 sulphuric acid, offering phenomena, in the investigation of which 

 the author is at present engaged. 



With reference to the presence of these substances in the state of 

 vapour in oil- and coal-gas, the means of ascertaining it and the 

 quantity are pointed out, in the peculiar action of sulphuric acid, 

 causing their perfect condensation, and in the solvent powers over 

 them possessed by fixed and volatile oils, &c. ; the requisite precau- 

 tions for their proper application being pointed out. Oil- gas was 

 found to be saturated with many of these vapours : coal-gas also 

 contained a portion of them. 



The paper concludes with a short reference to the probable uses 

 of the fluid, as originally obtained. If put into gas burning with a 

 blue flame, it makes it produce a bright white flame ; it is an excel- 

 lent solvent of caoutchouc ; it will answer all the purposes to which 

 essential oils are applied as solvents ; and having applied that portion 

 of it which, though a liquid at common temperatures and under a pres- 

 sure of two or three atmospheres, is a gas under any diminished pres- 

 sure, as fuel to a lamp ; the author has shown the possibility of such 

 an application, if at any time such knowledge and command of the 

 decomposition of oil or coal by heat should be obtained, as would 

 enable us to furnish the substance in abundance. 



Account of the Repetition of M. Arago's Experiments on the Magne- 

 tism manifested by various Substances during the Act of Rotation. 

 By C. Babbage, Esq. F.R.S. and J. F. W. Herschel, Esq. Sec.R.S. 

 Read June 16, 1825. [Phil. Trans. 1825,^. 467.] 



The experiments of M. Arago having excited much interest, the 

 authors of this communication were induced to erect an apparatus 

 for their verification ; and after a few trials they succeeded in causing 



