18 BULLETIN 102, PART 4, UNITED STATES NATIONAL MUSEUM. 
briquetting of low-grade coals, and to a limited degree around the 
manufacture of domestic “coke.” 
Producer gas is the result of the complete gasification of coal 
under the action of a mixture of air and steam. 1 Both high-grade 
and low-grade coals may be employed in its manufacture and the 
gas may be produced with or without the recovery of the by-products, 
ammonia, benzol, and tar. Most of the foreign by-products producer- 
plants, however, at least before the war, made adequate recovery of 
the ammonia only. The producer principle is not only successfully 
applied to central plants manufacturing gas for transmission as such 
or for the generation of electricity; but it is also employed in smaller 
and more mobile installations, known as suction plants, in which the 
gas-producer and gas-engine are a single unit. The suction plant, 
therefore, adapts raw coal to immediate use in the internal combus- 
tion engine, combining the efficiency of the latter with the mobility 
of the steam engine. Thus producer-gas is suitable not only for large 
service stations, but also for small industrial plants and even for 
marine engines and locomotives. The manufacture of producer-gas 
from coke, peat, lignite, and high-ash mine refuse has become so 
thoroughly established on the continent as to be a commonplace 
procedure. The widespread use abroad of the producer gas principle 
has brought into competition with high-grade coals used as such the 
low-grade coals and coallike substances needed to supplement a 
limited fuel supply. 
The briquetting of low-grade lignitic coals and coal slack has been 
successfully practiced in Germany and other European countries for 
over 30 years, thus, together with the results attained by producer 
gas, bringing into service types of coal largely unused in the United 
States. A number of special forms of fuel coke, approximating 
artificial anthracite, have met with some measure of success, especially 
in England, where they are sold under the trade names of coalite, 
char co, coalexld, and others. 
As a war measure, the belligerent countries of Europe have been 
forced to take radical steps in order to insure an advantageous use 
of their coal resources. The French and Italian Governments have 
assumed complete control of distribution. In May, 1917, the 
Russian provisional Government took over the coal mines of that 
country for the purpose of controlling distribution and prices. Early 
in the war, Germany centralized the entire coal industry under 
Government control and a recent report states that the use of 
raw coal has been forbidden. In England, the coal mines are 
under full Government authority and in addition a board of fuel 
research has been established which is recognizing both the economic 
1 It is strictly speaking modified or semi water-gas, lower in calorific value than water-gas proper which 
is made by gasifying coke or anthracite under the action of steam. 
