. The Philosophical magazine; a journal of theoretical, experimental and applied physics. S is a double screen of po-lished tin J A is an argand burner consisting of two concentricrings perforated with orifices for the escape of the gas; C is aheated copper ball; the tube 11 leads to a gas-holder containingtiie gas to be examined. When the ball C is placed on theargand burner, it of course heats the air in contact with it; anascending current is established, which acts on the pile as inthe experiments last described. It was found necessary toneutralize this radiation from the heated air, and f
. The Philosophical magazine; a journal of theoretical, experimental and applied physics. S is a double screen of po-lished tin J A is an argand burner consisting of two concentricrings perforated with orifices for the escape of the gas; C is aheated copper ball; the tube 11 leads to a gas-holder containingtiie gas to be examined. When the ball C is placed on theargand burner, it of course heats the air in contact with it; anascending current is established, which acts on the pile as inthe experiments last described. It was found necessary toneutralize this radiation from the heated air, and for this pur-pose a large Leslies cube L, filled with water a few degreesabove the temj)erature of the air, was allowed to act on the op-posite face of the pile. Wlun the needle was thus brought to zero, the cock of the gas-holder was turned on ; the gas ])assed through the burner, came into contact with the ball, and ascended afterwards in a heated column iti front of the pile. The galvanometer was now * La TliermucliroBL, p. !>4. Radiation of Heat by Gases and Vapours. 279 Fie. observed, and the limit of the arc through which its needle wasurged was noted. It is needless to remark that the ball wasentirely hidden by the screen from the thermo-electric pile,and that, even were this not the case, the mode of neutraliza-tion adopted would still give us the pure action of the gas. The results of the experiments are given in the followingTable, the figure appended to the name of each gas markingthe number of degrees through which the radiation from thelatter urged the needle of the galvanometer*:— Air 0 Oxygen .... Nitrogen 00 Hydrogen .Carbonic oxide 012 Carbonic acid . 18 Nitrous oxide . 29 Olefiant gas 53 The radiation from air, it will be remembered, was neutralizedby the large Leslies cube, and hence the 0° attached to it merelydenotes that the propulsion of air from the gas-holder throughthe argand burner did not augment the effect. Oxygen, hydro- • I have also re
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