37 2 Mr. Children’s experiments 
closely round them. All the wires were of pure soft iron, 
and the part containing the diamond powder, was enveloped 
by thin leaves of talc. Thus arranged, the apparatus was 
placed in the electrical circuit, when it soon became red hot, 
and was kept so for six minutes. The ignition was so far 
from intense, that few who witnessed the experiment, ex- 
pected, I believe, any decisive result. On opening the wire, 
however, Mr. Pf.pys found that the whole of the diamond 
had disappeared ; the interior surface of the iron had fused 
into numerous cavities, notwithstanding the very moderate 
heat to which it had been exposed ; and all that part which 
had been in contact with the diamond was converted into 
perfect blistered steel. A portion of it being heated red and 
plunged into water, became so hard as to resist the file, and 
to scratch glass. This result is conclusive, for as the contact 
of any carbonaceous substance, except the included diamond, 
was effectually guarded against, to that alone can the change 
produced in the iron be referred. This experiment will also 
probably be deemed fatal to the opinion of those mineralo- 
gists (if any do still maintain that opinion,) who class the 
diamond with substances of the siliceous genus. 
When dry caustic potash was exposed to the intense heat 
between the two pieces of charcoal, it fused, and appeared to 
decompose, throwing off a large flame of the peculiar purple 
red colour, that attends the combustion of potassium. When 
moist caustic potash was placed in the circuit, the water only 
was decomposed. 
I endeavoured to ascertain if there be any difference in the 
degree of heat produced at either pole of the battery, by plac- 
ing two small earthen-ware cups, each containing an equal 
