48 Mr. W. R. Grove o?^ the Electricity of the Blowpipe Flame. 



querePs recent paper that M. Becquerel, sen. has used it as a 

 means of adventitiously heating a spiral placed in another 

 flame. 



Two platinum wires of 6 inches long and y^th of an inch dia- 

 meter have their ends formed into coils of ^th of an inch long and 

 ■wide ; these wires are attached to copper wires insulated by glass 

 stands, and having their further exti*emities connected with a 

 galvanometer. My galvanometer is by Ruhmkorf ; the wive is 

 not as long as those now constructed, being only 544 feet, but 

 I have magnetized the needles so as to render them highly 

 astatic; they take four minutes to make one oscillation. 



An adfhtional binding screw is connected with the wire at 54 

 feet, so that I can ascertain by the same instrument the eficct 

 of a slighter resistance. 



When the flame of a spirit-lamp is urged by the blowpipe, 

 one of the above-mentioned coils is placed in the full yellow flame 

 just beyond the apex of the blue cone, and the other near the 

 orifice of the brass jet, or at what may be called the root of the 

 flame, just above the base of the blue cone, the distance between 

 the two coils being 2| inches. The coil in the full flame is at a 

 white heat brilliantly incandescent, the coil near the orifice or at 

 the commencement of the flame is cherry-red. The galvano- 

 meter is deflected to an average of 6°, the coil near the orifice or 

 at the root of the flame being jjositive, or related to the further 

 coil as zinc to platinum in the voltaic trough. On reversing the 

 position of the wires, the galvanometer is deflected 6° in the 

 opposite direction. 



This current is not due to thermo-electricity excited in the 

 wires at the point of junction of the platinum and copper, for it 

 is unaltered in direction by a powerful thermo-current excited 

 in these by heating the points of junction by another spirit- 

 lamp. 



By making this thermo-current aid or counteract the flame- 

 current, a slight diff'erence in degree is perceptible in the deflec- 

 tion according as the point of junction of the one or other wire 

 is heated, but no difi'erence in direction. 



The flame-current, moreover, scarcely affects the short wired 

 galvanometer, while the thermo-current of copper and platinum 

 whirls the needle to 90°. 



It is not a thermo-electric current arising from the unequal 

 heating of the two coils, for it is in the same direction when the 

 further coil is removed from the full flame so as to be less heated 

 than the coil at the root of the flame. It is also different in 

 direction from the thermo-current produced by unequally heating 

 the coils in similar parts of the flame, or the current described 

 by M. Buff", and to which he ascribes the electricity of flame. 



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