MINISTRY OF SCIENTIZATION |
| DIRECTOR Baxter Schuchard |
ABOUT
" Mr. Robert Mallet communicated a notice of the discovery of the property of the light emitted by incandescent coke to blacken photogenic paper; and propose it as a substitute for solar light, or that from the oxy-hydrogen blowpipe with lime.
" One of the most important applications of the photogenic process, as yet suggested, is its adaptation to the self-registering of long continued instrumental observations. Unless, however, an artificial light of a simple and inexpensive character can be found to supply the place of solar light at night, the utility of this application will be much limited.
" Few artificial lights emit enough of the chemical rays to act with certainty on the prepared paper; while those which are known to act well, as the oxyhydrogen lime light, are expensive and difficult to manage. A considerable time since the author discovered that the light emitted by incandescent coke at the - Twyer- (or aperture by which the blast is admitted) of a cupola or furnace for melting cast iron, contained the chemical rays in abundance ; and on lately trying the effect of this light on the prepared paper, he found it was intensely blackened in about forty-five seconds. In the single experiment made, the heat, which was considerable, was not separated from the light; but the author purposed to make further experiments, in which this precaution will be attended to.
" There is no difficulty to be apprehended in contriving an apparatus to burn a small quantity of coke at a high temperature. A diagram of an apparatus for this purpose was shown. It consists of a vertical tube, nine inches in diameter, lined with refractory clay, and closed at top and bottom. There is a grating about one foot from the bottom, a little above which are two opposite holes, into one of which an air blast from a revolving fanner is projected through the coke, with which the whole tube is filled. The flame passes out at the opposite hole, through a tube so contrived, as to heat the blast of air to a temperature of 500°, just before it enters the coke fire.
" The light from the former lateral aperture is that proposed to be used, and issues through a plate of mica or glass opposite to it. This aperture forms part of the conductory tube for the blast, which (by passing into the coke in a direction opposite to that in which the light is emitted) keeps the illuminating surface of coke clear from ashes; these are received below the grating, and by a diversion of part of the blast, are blown into the chimney which receives the other products of the combustion.
" As the vertical tube is close above, the combustion cannot proceed upwards, while the coke with which it is filled constantly drops down to supply the place of that consumed, on the principle of the ancient furnaces, called - athanors- by the earlier chemists.
" The only difficulty to be apprehended in the use of coke, is the collection of slag from the fusion of its earthy and ferruginous constituents ; however the author does not consider that this accumulation during the period from sunset to sunrise, in mid-winter, would materially interfere with its action."