194 
Scientific Intelligence. 
two last numbers, have excited much interest, we shall lay be- 
fore our readers the following observations which have been pre- 
viously made on the subject, and v/hich have been sent us by a 
correspondent. Carbon, says Sir H. Davy, whether coherent 
as charcoal, or in powder, is infusible by any heat that has hi- 
therto been applied. I have exposed it to the powers of intense 
ignition of different voltaic batteries ; that of Mr Children, men- 
tioned page 151., one of 40 double plates 18 inches square, and 
the battery of 2000 double plates, both in vacuo and in the com- 
pressed gases, on which it had no power of chemical action. A 
little hydrogen was given off from it ; it slowly volatilized in these 
experiments, and the part remaining was much harder than be- 
fore, so as in one case to scratch glass ; the lustre was greater ; but 
its other properties were unaltered ; there was no appearance of 
fusion. Dr Clarke exposed a diamond of 6 carats, of an amber 
colour, to the flame of the gas blowpipe. It became colourless and 
transparent, — after this it became white and opake, and by con- 
tinuing the heat, it was entirely volatilized in about three minutes. 
Glance-coal from the Calton Hill, according to Mr Sivright’s ex- 
periments, when heated in the focus of an 18 inch silvered mirror, 
was slowly volatilised, but there was no appearance of fusion. 
The substance found under the gas retorts was volatilized in 
the same way with a slight smell of ether, but it was not fused. 
Dr Clark says, that the fusion of plumbago with the gas blow- 
pipe was attended with a vivid scintillation. The surface was 
covered with a number of minute globules ; some of which ex- 
hibited a limpid and highly transparent glass, others a glass of 
a brown hue ; the larger globules being jet black and opake, 
with a dark metallic lustre. With the common blowpipe, Mr 
Sivright found that black globules were formed on the surface 
of plumbago, but no transparent ones. In the focus of the 
mirror it became brown, with ‘small white specks and black 
globules on its surface. The globules are probably an iron 
slag. They are hard enough to scratch glass. The white 
specks are perhaps silica, or some earth which the heat obtain- 
ed in this way is not sufficient to fuse.” 
27. Cagnard de la I" out's Eocperimeyits on the Vaporisation 
Fluids. — In our last volume, p. 199> we gave a general no- 
tice of these curious experiments. M. Cognard de la Tour has 
