nferior
to wood-gas in illuminating power.

It is essential, that well-dried peat be employed, and the waste heat
from the retorts may serve in part, at least, for the drying.

The retorts must be of a good conducting material; therefore cast iron
is better than clay. They are made of the [symbol: D] form, and must be
relatively larger than those used for coal. A retort of two feet width,
one foot depth, and 8 to 9 feet length, must receive but 100 lbs. of
peat at a charge.

The quantity of gas yielded in a given time, is much greater than from
bituminous coal. From retorts of the size just named, 8000 to 9000 cubic
feet of gas are delivered in 24 hours. The exit pipes must, therefore,
be large, not less than 5 to 6 inches, and the coolers must be much more
effective than is needful for coal gas, in order to separate from it the
tarry matters.

The number of retorts requisite to furnish a given volume of gas, is
much less than in the manufacture from coal. On the other hand, the
dimensions of the furnace are considerably greater, because the
consumption of fuel must be more rapid, in order to supply the heat,
which is carried off by the copious formation of gas.

Gas may be made from peat at a comparatively low temperature, but its
illuminating power is then trifling. At a red heat alone can we procure
a gas of good quality.

The chief impurity of peat-gas is carbonic acid: this amounts to 25 to
30 _per cent._ of the gas before purification, and if the peat be
insufficiently dried, it is considerably more. The quantity of slaked
lime that is consumed in purifying, is therefore much greater than is
needed for coal-gas, and is an expensive item in the making of peat-gas.

While wood-gas is practically free from sulphur compounds and ammonia,
peat-gas may contain them both, especially the latter, in quantity that
depends upon the composition of the peat, which, as regards sulphur and
nitrogen, is very variable.

Peat-gas is denser than coal-gas, and therefore cannot be burned to
advantage except from considerably wider orifices than answer for the
latter, and under slight pressure.

The above statements show the absurdity of judging of the value of peat
as a source of gas, by the results of trials made in gas works arranged
for bituminous coal.

As to the yield of gas we have the following data, weights and measures
being English:--

100 lbs. of peat of medium quality from Munich, gave REISSIG 303 cub. ft.