GEOLOGICAL METHODS IN EARLIER DAYS 31 



much time had been spent in Greene ; there remained the larger county 

 of Washington and a great part of Allegheny to be studied. 



The problems in Washington, though different, were equally per- 

 plexing for a time. Exposures were better, longer continuous sections 

 were secured, but new members came in while familiar ones dropped 

 out. We were firm believers in variation of intervals between coal 

 beds, but were not prepared for the variations which had been accom- 

 plished in the deeply buried portions of the section within northern 

 Greene and southern Washington and which were revealed under an 

 anticline in Washington. The imperfect record of a coal shaft reach- 

 ing the Pittsburgh coal bed removed all doubts and filled us with in- 

 tense respect for such records. The work in this county was not diffi- 

 cult as the section had been mastered ; the especial burden being to cover 

 the region in detail before snowfall, as the report must be ready for the 

 printer before adjournment of Legislature. 



During this season's work our attention was concentrated upon cor- 

 relation and economic questions; there was no time for studies con- 

 cerning matters of purely scientific interest. So intent were we in con- 

 sideration of those subjects that we neglected to make notes of features 

 which are all-important in their bearing on problems relating to coal 

 and coal beds. Having sinned in this way, it is not for me to cast stones 

 at any one for a similar sin, provided it has been committed under 

 similar conditions. 



A serious difficulty encountered by geologists in the earlier work was 

 the inaccuracy of maps. One illustration suffices. In Fayette and 

 Westmoreland Counties of Pennsylvania, I made use of maps which the 

 county surveyors regarded as the least inaccurate. Professor Lesley had 

 done some geological work in those counties and had discovered defects 

 in the maps, which disturbed him greatly. He chose worse maps, cor- 

 rected some errors in them and transferred my outcrop lines to the new 

 base. The creations were put on the stone and proofs were sent to me. 

 A single glance aroused feelings too deep for utterance and the proofs 

 were returned without change. No doubt many other geologists can 

 relate a similar experience. 



Geologists, entering on field work within the last score of years, 

 know little of the difficulties attending exploration forty or more years 

 ago, especially in coal areas, where the effort was to trace thin deposits 

 throughout extensive areas; though exception should be made in favor 

 of those laboring in similar areas at the far west, where dependence 

 must still be placed on natural exposures. In by far the greater part 

 of the country the structural geology has been worked out during more 

 or less reconnoissances, so that when the reviser entered tlie field he 

 found everything so simple that he was astonished that any one should 

 have been perplexed and still more astonished that mistakes were 



