400 Scientific puaenee 
designated depth. The problem is far too difficult a one to be 
disposed of in so summary a manner, especially as we had at that 
time scarcely more than commenced examinations in Nebraska. 
A few days after, we learned that borings had already been made 
at Omaha and Nebra ska City to the depth of an hundred feet 
without finding a workable bed of coal. From these facts, and 
isso 
‘decide i ‘. ‘regar rd to the actual depth at which the equivalents of 
the lower Coal-measure strata would be reached there, and that 
actual boring alone could decide whether coal existed there or not. 
is conclusion was discussed by us in camp at the close of 
ur examinations, in the presence of the whole party, Dr. 
- cluded, and I supposed was understood b 
My vi Cc 
ews in regard to the Coal-measures of Io owa, so far as they 
are yet formed, may be learned by rae: Ba articles in this 
Journal, and my reports. See First and Second Annu al E188. 
urnal, 
given attention to fossil lamellibranchiates cannot fail to have 
observed that whenever the shell-substance is preserved at all, it is 
universally thin, even in large specimens; too thin indeed to have 
