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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 incan- 
descent coke, at the “‘Twyer” (or aperture by which the 
blast is admitted) ofa 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 conside- 
rable, was not separated from the light; but the author pur- 
posed 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 tempe- 
rature. 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 pro- 
posed to be used, and issues through a plate of mica or 
glass opposite toit. This aperture forms part of the con- 
ductory 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 can- 
2c 
