retort itself--which is also fitted with baffle plates--to the front
of the retort, whence the fixed gases escape by the stand pipe to the
hydraulic main, and the rich gas thus formed is used either to enrich
coal gas or is mixed with water gas made in a separate generator. In
some forms the water gas is passed with the oil through the retort. In
such a process, the complete breaking down of some of the heavy
hydrocarbons takes place, and the superheated steam, acting on the
carbon so liberated, forms water gas which bears the lower
hydrocarbons formed with it; but inasmuch as oil is not an economical
source of carbon for the production of water gas, this would probably
make the cost of production higher than necessary. This system has
been extensively tried, and indeed used to a certain extent, but the
results have not been altogether satisfactory, one of the troubles
which have had to be contended with being choking of the retorts.

Of the intermittent processes, the one most in use in America is the
"Lowe," in which the coke or anthracite is heated to incandescence in
a generator lined with firebrick, by an air blast, the heated products
of combustion as they leave the generator and enter the superheaters
being supplied with more air, which causes the combustion of the
carbon monoxide present in the producer gas, and heats up the
firebrick "baffles" with which the superheater is filled. When the
necessary temperature of fuel and superheater has been reached, the
air blasts are cut off, and steam is blown through the generator,
forming water gas, which meets the enriching oil at the top of the
first superheater, called the 'carbureter,' and carries the vapors
with it through the main superheater, where the "fixing" of the
hydrocarbons takes place.

The chief advantage of this apparatus is that the enormous