217 
IJiii. long, because the clay is a non-conductor of heat 
and would not injure the platinum, when heated to 
redness. Into this platinum crucible I introduced 1 
gramme of coal in a fine state of division, which was 
ignited, after being placed on its stand, by a fuse such as 
that used by Mr. Lewis Thompson, and the whole covered by 
an inverted wide glass test tube 6iu. long by l^in. diame- 
ter, to the bottom of which was attached a piece of narrow 
tubing lin. long by fin. in diameter. Over this tube was 
drawn a piece of indiarubber tubing, the free end of which 
was turned over on itself, and through this rubber was 
passed a glass or thin copper tube (preferably the latter) ter- 
minating with a stop-cock. 
When the fuse is ignited the mouth of the test tube is 
pushed over the brass springs, thus enclosing the platinum 
crucible containing the coal, on the diving-bell principle, 
and the whole is then sunk into the cylinder, containing 
either 1,934 or 2,000 grammes of water, the temperature 
of which has previously been taken by a delicate 
thermometer. A stream of oxygen from a gas holder 
or gas bag is then allowed to flow slowly through the 
test tube downwards, making its escape at the mouth 
and bubbling through the water. It is necessary to 
commence the combustion by having the movable tube 
which penetrates the bottom of the test tube drawn 
well up so as to have a complete atmosphere of oxygen in 
the test tube until most of the volatile matter of the coal 
is consumed. The movable tube is then gradually pushed 
down till it comes to the mouth of the platinum crucible; a 
slow circular movement is then given to it by the hand 
till the whole of the fixed carbon of the coal is consumed, 
which is rapidly done under the stream of oxygen impinging 
on it. The ash is then left as a number of fused globules, 
many of them adhering to the crucible, having been 
completely fused by the intense heat of the combustion. 
