THE LOWER COAL MEASURES. 147 
amounts of the several chemical elements and compounds in any coal 
are, of course, a definite quantity, the amounts reported in analyses as 
fixed carbon and volatile matter depend to a certain extent upon the 
details of the methods used in determining them. The method used by 
the Chemist of the Survey, Professor N. W. Lord, gives somewhat 
lower figures for the fixed carbon of our coals than those that have been 
generally accepted hitherto. A synopsis of the methods employed will 
be found in a later portion of this volume. 
The remaining substances reported in our analyses are moist- 
ure, ash and sulphur. While these substances are never absent from 
coal, they are found in it in very different amounts, and, speaking 
generally, any increase in proportion above the lowest figures that are 
found, is to be counted as a detriment and drawback in the ratio of 
such increase. But even here the results af analysis cannot be used as 
an absolute guide in determining the value of any particular coal. 
Other things being equal, the smaller the amount of ash, sulphur and 
moisture, the better the coal, but the saving clause is of wide extent 
and application. The physical character of the coal is involved in it, 
and it is often true that firmness and tenacity in a coal will more than 
compensate in the general judgment for some inferiority in composition. 
Chemists are not entirely agreed as to the proper method of 
determining the absolute efficiency of a coal. The result of many 
determinations has seemed to make the heating power depend upon the 
fixed carbon alone, but other experiments are construed as proving that 
the heating power is proportioned to the total amount of carbon of the 
coal, that of the volatile matter being included with the fixed carbon. 
It is no doubt true that the amount of fixed carbon in a coal furnishes 
an approximate gauge of its absolute heating power. 
There are few coal mines in the State in which good specimens of 
coal cannot be found, and there are none that do not contain some coal 
of inferior quality. The instances are very rare in which the quality of 
an Ohio mine can be safely determined by the analysis of a single, so- 
called average specimen. But many of the analyses now current were 
made from single pieces, and often from small ones at that, selected to 
show the very best quality of the mine. ‘The results of such analysis 
are, as a rule, altogether too favorable, and they are not to be depended 
on for practical guidance. They naturally represent the best portions 
of their respective seams, but for practical service, a knowledge of the 
