PREFACE. 
The plan of a volume to be entitled “ Economic Geology,” and which should 
form one of the final reports of the Geological Survey of the State then in progress, 
was announced as early as 1870 by my predecessor, Professor J. 8S. Newberry. The 
scope of the volume as originally designed can be seen in his first formal an- 
nouncement of it, Report of Progress, 1870, page 12. Its prospective contents are 
there stated in the following terms, viz.: “The geology and technology (mining, 
manufacture and uses) of our Coals, Iron Ores, Clays, Salts, Limes, Hydraulic 
Cements, Petroleum, Gypsum, Building Stones, etc., ete.” 
Frequent references to this volume are made in subsequent reports of the Sur- 
vey. For example, in volume II, Geology of Ohio, page XIII, Professor Newberry 
speaks of it as “intended to include an exhaustive and accurate review of all our 
mineral staples, Coal, Iron, Peat, Clay, Salt, Oil, Building Material, etc.” He further 
describes it as designed “to determine the quality, uses and best methods of manu- 
facture of our mineral staples, not only by means of the ordinary chemical analyses, 
but by carefully gathering the results of all the trials to which they have been sub- 
jected in real life and by original experiments made with an amount of material, 
and under such conditions as would afford a practical and working test of each.” 
To many, and probably to most of that portion of our citizens who have taken a 
definite interest in the progress of the Survey, the volume thus announced has 
seemed certain to be the most interesting and valuable of the entire series, and, 
accordingly, after the publication of the reports of the Survey had been interrupted 
for several years through the failure of successive legislatures to provide for the 
issue of the third volume of Paleontology, a bill to complete the volume on Economic 
Geology was passéd by the Legislature in 1882, with but little opposition, and, in 1883, 
provision was made to publish it when completed. 
The volume herewith presented derives its title as well as its general scope from > 
the plan projected by Professor Newberry, but if this plan could have been worked 
out by its distinguished author the result would have been a very different volume 
from the present, and, assuredly, a much more valuable one. Of the field mapped 
out in the comprehensive program already quoted, there are entire sections into 
which I have not been able to enter, and in those subjects which the present volume 
discusses, the limitations arising in part from want of time and means for investiga- 
tion are to be found on every page. 3 
In treating the subjects included in the present volume, I have steadily 
endeavored to keep within the limits imposed by the title and plan of the work as 
fixed by my predecessor and by the action of the Legislature, and, therefore, no 
’ discussion of the general geology of the State, as such, is to be looked for in these 
pages. But inasmuch as our mineral wealth is chiefly centered in the Coal 
Measures, a discussion of the economic elements of the Ohio scale will largely con- 
sist in a discussion of the geology of the Coal Measures, and principally of the 
