Account of the Repetition of M. Arago's Experiments on the Magnetism Manifested by Various Substances during the Act of Rotation

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 oiland 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.