130 | GEOLOGY OF OHIO. 
The second system designates the seams by letters or by numbers. 
Lesley. in his “Manual of Coal and its Topography” as well as in earlier 
contributions to the First Pennsylvania Survey, made use of letters, 
styling the Brookville coal, coal A, the Clarion coal, coal B, ete., but 
in the reports of the Second Pennsylvania Survey, now in progress, he 
emphatically discards and repudiates this method. (Q 2, Preface, p. 
xxix. Note.) 
Newberry introduced the use of numbers for the same purpose in 
his reports on the Ohio coal-fields. The system first appears in the Re- 
port of Progress for 1870 (p. 26 et al.), but it was considerably modi- 
fied in his more formal and extended treatment of the subject in volume 
II of the final reports (pp. 180-131.) The Wellston coal is here referred 
to. There is much to be said in favor of the use of numbers in such a 
classification. They certainly afford the most convenient designations. 
Number 5 is spoken and written more easily than Lower Kittanning. 
Furthermore, the number definitely suggests the position of the 
seam in the series, while the local name can do so only in an indirect 
way. When we identify a coal seam as the Lower Kittanning, we 
assign to it as definite a place in the series as a number could do, but we 
are obliged to call to mind a greater number of facts in reaching the 
conclusion. Lesley’s objections to letters and numbers in the passage 
referred to above, do not seem well taken. They are valid against a 
system of numbers that is applied before the facts in regard to the 
series are known, but they will hold with equal force against any other 
system of identifying and naming the beds of different localities under 
like condition. 
It is certain, that no important and widely extended coal seam ex- 
ists in Western Pennsylvania that has not been taken account of by the 
Survey now in progress there. Such aseam could not have been missed 
alike in outcrop and in boring during the protracted and thorough ex- 
aminations, scientific and practical, to which the coal measures of that 
State have been subjected. If numbers or letters were now used to 
designate these coal seams, it would never be necessary to change them. 
Any sporadic or local deposit hereafter discovered could easily be inter- 
calated in the numerical scale as it would need to be in the geological 
column. ; 
The strongest objection that appears is, that such numbers might 
stand in the way of correlating the series of widely separated fields, as 
