4^0 Dr. Ure on the ultimate analysis of 
Many chemists, particularly in this country, have employed 
the heat of a spirit lamp, instead of that produced by the 
combustion of charcoal, for igniting the tube in which the 
mixed materials are placed. I have compared very carefully 
both methods of heating, and find that for many bodies, such 
as coal, and resin, which abound in carbon, the flame of the 
lamp is insufficient ; while its application being confined at 
once to a small portion of the tube, that uniform ignition of 
the whole, desirable towards the close of the experiment, 
cannot be obtained. I was hence led to contrive a peculiar 
form of furnace, in which, with a handful of charcoal, re- 
duced to bits about the size of small filberts, an experiment 
may be completed, without anxiety or trouble, in the space of 
half an hour. Since I have operated with this instrument, 
the results on the same body have been much more con- 
sistent, than those previously obtained with the lamp ; and it 
is so convenient, that I have sometimes finished eight ex- 
periments in a day. 
Fig. i . (Plate L.) represents the whole apparatus, as when 
in action. Fig. a is a horizontal section of the furnace, in 
which we perceive a semi-cylinder of thin sheet iron, about 8 
inches long and 3% wide, perforated with holes, and resting 
on the edge of a hollow prism of tin-plate, represented more 
distinctly in fig. 3, where n shows a slit, through which the 
sealed end of the glass tube may be made to project, on oc- 
casion. z, is a handle attached to the semi-cylinder, by which 
it may be slid backwards or forwards, and removed at the 
end of the process, d, is a sheath of platinum foil, which 
serves, by aid of a wire laid across, to support the middle of 
the tube, when it is softened by ignition. At g , the plates 
