5^5 
Combustion of the Diamond. 
the three experiments was there any distinct appearance of 
carbonization, when the process was stopped in consequence 
of the impurity of the gas; though the diamonds were of 
various colours and different lustres. 
A piece of plumbago from Borrowdale in Cumberland, 
weighing two grains, was exposed in the focus in the same 
manner as the diamond in the first and second experiments, 
having been previously heated red ; the quantity of oxygene 
gas employed was 8.5 cubical inches: more than half the 
plumbago remained unconsumed, and during the combustion 
some brown ashes were produced. The phenomena in this 
experiment were very different from those observed in the 
experiments on the diamond, the gas became clouded during 
the process, and there was a considerable deposition of dew 
on the interior of the globe. When the original temperature 
of the globe was restored, and the stop-cock opened, 96.6 grains 
of mercury entered, and drops of moisture even were observed 
condensed on the sides of the vessel. 
In the second series of experiments, charcoal formed by the 
action of sulphuric acid on oil of turpentine, and some pro- 
duced during the formation of sulphuric ether, from which 
nitric acid had been distilled, and which afterwards had been 
strongly ignited, and charcoal of oak which had undergone 
the same process, were used. 
Three grains of the charcoal from turpentine were em- 
ployed, 2.5 of that from alcohol, and five grains of the charcoal 
of the oak : in all these instances of combustion the gas be- 
came clouded during the combustion, and when the original 
temperature of the globe was restored, moisture was found 
condensed in the interior ; much the largest quantity in the 
MDCCCXIV. 4 D 
