MINERAL INDUSTRIES OF THE UNITED STATES — COAL PRODUCTS. 11 
hive oven is heated by the combustion of its oven gases within the 
inclosure while the bench retort is heated from an external source 
commonly derived from its own coke of earlier yield; and lastly 
the production of first-quality coke is the one and only aim of the 
beehive operations whereas the bench retort includes the production 
of first-quality gas along with the incidental saving of a more or 
less nondescript coke and possible eventualities in all of the other 
coal distillation products : 1 
In the case of the gas bench, the coke yield is of a quality un- 
suited to metallurgical use; in the beehive oven on the other hand 
only a small fraction of the gas generated is necessary under 
adequate conditions to maintain the temperature necessary to dis- 
tillation. Accordingly two industries exactly complementary in 
fundamental character, were obliged to travel their own courses of 
separate wastefulness side by side for upward of half a century, 
pending the evolution of a system combining the coke advantages 
of the beehive oven with the distillate saving of the retort type. 
The problem offered manifold complications in the form of opera- 
tive efficiency, and despite the heralding of various attempted solu- 
tions, it was not until the decade beginning in 1880 that installations 
fully adequate to the test of practice were established. Credit for 
the accomplishment belongs unqualifiedly to German enterprise. 
Once established, advance was rapid, and the coming of the present 
century found an extensive coal by-product industry centered in 
Germany and the beehive oven battery supplanted throughout con- 
tinental Europe by the so-called by-product coke plant. 
The aim in the by-product coke plant is, as its name implies, the 
generation of a coke in conformance with the standards set by the 
beehive oven, coupled with the saving of volatile matters effected in 
connection with the gas retort. In principle the modern procedure 
is identical with that of the gas bench, the essential difference origi- 
nating in the practice of employing retorts of many times the 
capacity of the gas retort with a proportionate rearrangement and 
elaboration of plant construction throughout. The retort ovens 
1 The beginning in the history of the two developments may be of interest in 
passing. Back as far as 1817 the Pittsburgh Chamber of Commerce, noting the 
rapidity with which the wood supplies available for the preparation of char- 
coal fuel, the accepted metallurgical fuel at that time, were becoming depleted, 
commissioned a representative to investigate a rumored usage in England of 
a product of similar derivation to charcoal only from bituminous coal instead 
of from wood. The rumor was substantiated and presently the product known 
as coke began to find favor among American metallurgists. From these be- 
ginnings the metallurgical use of coke has grown steadily to the present vast 
proportions involving an average of over a million tons of coal a week in its 
preparation. The uses of coal gas began further back in 1792 when William 
Murdock illuminated his home in Redruth, England, with the distillate from 
coal in a retort which he devised for the purpose. 
