144 
Progress in Science. 
pipe-shank, the end of the wire being bent upwards and formed into hooks so 
as to hang on the edge of the flower-pot (Fig. 3), or three pipe-covered wires, 
suspended in the position of the ribs of a crucible jacket. The former is 
necessary for small crucibles. The flower-pot also makes an excellent lamp- 
screen, for steadying and concentrating the flame under evaporating basins, 
&c. A small flower-pot with wire gauze tied over the top is a very effective 
low temperature lamp when the gas is lighted before the gauze. If the gas is 
lighted above the gauze an argand lamp giving a large clear blue flame is ob- 
tained. In the latter case a common burner can be used. Having occasion 
to determine the volatile matter of a coal, and riot having at hand the usual 
elaborate arrangements, Mr. Hardman thought of the schoolboy’s method of 
manufacturing coal-gas. The retort he uses is a common clay tobacco-pipe. 
A piece of coal is put in, the top is luted with clay, and the pipe is inserted in 
the fire-grate with the stem projecting. Presently a dense smoke issues from 
it, and and a match being applied a veritable gas light — but not “ 16-candle ” 
— results. On opening the luting a piece of coke is found in the pipe. It is 
obvious that it is only necessary to weigh the pipe and contents before and 
after the operation, and we have the volatile matter and coke determined. 
The larger the pipe the better. The coal must be broken small, but not pow- 
dered. The pipe is weighed, then filled with the coal aud weighed again to 
obtain weight of coal. Then inside the top is fitted a circular piece of writing- 
paper, the use of which is to prevent any of the luting getting down among 
the coal, where it could not be removed, and would falsify the last weighing. 
The top is luted with moist fireclay, or with the cement used for luting the 
covers of gas retorts, and the pipe being placed in a common coal fire or in a 
gas furnace from ten to twenty minutes completes the operation. When cool 
the luting is carefully taken off and the charred paper removed. The pipe and 
contents being then weighed, the loss gives the volatile matter, the same 
weighing, of course, determining the coke. If a very exadt determination is 
required, a quantity of the coal may be broken small, well mixed together, 
and four pipes filled as above. They can all be ignited together in a fire, and 
weighed very quickly. The results will be found to agree very closely. This 
tobacco-pipe process has the great advantage of being very expeditiously per- 
formed — the whole experiment including weighings not occupying more than 
thirty minutes — and with very simple apparatus. 
