lo.x The American Geologist. June, isw 
In this state the attempts to correlate individual seam's have 
not proven to be successful and have led to much confusion. 
Recently ;i complexity, rather than a simplicity, has been 
round to exist, and it has become recognized thai the individ- 
ual licds of the I. owe i- ( !oal Measures, ;it Least in the [owa- M iss- 
oui'i field, are characteristically non-persistent. This was in 
some cases alluded to by the earlier worker-, but little stress 
w.-is placed upon it. Recently it has been elaborated quite 
fully and interpreted ns the result of the conditions of depo- 
sition; the Lower Coal Measures being regarded us marginal 
depositions, and the Upper Coal Measures as representing the 
marine beds which were deposited, in pari ;it least, contem- 
poraneously. 
Complexity of si ructure, due entirely to the non-persistenl 
character of the beds themselves rather than to deformations, 
has been so widely recognized in Iowa and .Missouri that it 
has been with extreme caution that particular coal seams have 
been correlated with those of other localities, and in no case 
hitherto described has the continuity of a single bed been as- 
certained to extend more than a few miles. Natural expos- 
ures and connecting sections along streams show that the 
Lower Coal Measures of Iowa are made up of a complex inter- 
locking series of heds of shales, sandstones and limestone-. 
with occasional coal seams. Although, as a rule, these are all 
prevailingly non-persistent, a few of the limestone hands and 
some of the sandstones have heen found to COVei" considerable 
areas. The individual coal seams, however, are generally 
quite limited in area] disl ribution. 
In marked contrast to this general character is a seam at 
present worked in Appanoose and adjoining counties in 
southern Iowa. As compared with other coal seams in the 
state, the extent of the one in question in quite exceptional. 
Its distribution so far as traced up to the present time is 
shown on the accompanying sketch map ( fig, I ). Tt is known 
to extend over a distance of nearly fifty miles north and south 
and at least Forty miles east and west. There is probably no 
other vein in the Lower Coal Measures of Iowa which extend- 
unbroken over an equal stretch of territory. Throughout it- 
extent it preserves nearly uniform characteristics which make 
its recognition easy and secure. 
