collier.] CLASSIFICATION OF YUKON COALS. 59 
stated that an anthracite has a fuel ratio above 10 and a bituminous coal 
has a fuel ratio between 1 and 5. There are two grades between the 
bituminous and the anthracite: Semianthracite, with a fuel ratio from 
about 7 to 10; and semibituminous, with a fuel ratio from 5 to 7. 
Cannel is a variety of bituminous coal which is characterized by a low 
fuel ratio, often less than 1. 
In distinguishing between the lignite and bituminous grades of coal 
the problem is more complex, and three elements must be considered: 
First, fuel ratio; second, content of water; and third, physical charac 
ter of the coal, as shown by the presence or absence of woody struc- 
ture. Dr. Hayes has suggested to the writer that a lignite may be 
distinguished from a bituminous coal by its having a water content 
above 10 per cent and a fuel ratio less than l. a The relation of the 
two elements can be expressed by the quotient of the water content 
divided by the fuel ratio. This might well be called the lignite ratio, 
and is above 10 for a lignite and less than 10 for a bituminous coal. 
By the use of this ratio, the physical character of the coal being neg- 
lected, it is found that nearly all the coals that have been classed as 
lignites by physical character alone fall readily into that class, while 
the bituminous coals are as certainly distinguished. 
As there is no definite dividing line between bituminous and anthra- 
cite, so the variation from lignite to bituminous is gradual, and an 
intermediate division or grade is often required between the typical 
lignite, with a water content above 15 per cent and a fuel ratio not 
above 0.5, and the typical bituminous coal, with a fuel ratio near 
1.5 and a water content under 7 per cent. If the above-mentioned 
lignite ratio be accepted as the basis of separation, it will be seen that 
typical lignites and typical bituminous coals can be recognized from 
their analyses by inspection. It is only in doubtful cases that the 
lignite ratio is required to determine the grade of the coal. The 
writer would suggest that, where a definite classification is required, 
doubtful cases in which the lignite ratio falls between 9 and 11 should 
be classed as intermediate between the lignites and the bituminous 
coals. 
In the grades of coal between bituminous and anthracite the terms 
semibituminous and semianthracite are both made use of as trade 
names in the United States. A logical classification and nomencla- 
ture would require a similar use of the terms semilignite and semi- 
bituminous for the grades of coal between lignite and bituminous. 
Such use seems to have been made of the term semibituminous in the 
coal fields of the Rocky Mountain region. 6 
« The same statement is made by J. A. Taff , Preliminary report on the Camden coal field of Arkan- 
sas: Twenty-first Ann. Rept. U. S. Geol. Survey, pt. 2, 1900, p. 326. 
frStorrs, S. L., Rocky Mountain coal fields: Twenty-second Ann. Rept. U. S. Geol. Survey, pt. 3, 
1902, p. 424. Hills, R. C, Coal fields of Colorado: Mineral Resources U. S. for 1892, U. S. Geol. Survey, 
1893, pp. 319-365. Knight, W. C, Coal fields of Wyoming: Sixteenth Ann. Rept. U. S. Geol. Survey, 
pt. 4, 1895, pp. 208-215. 
