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 perplexing 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 accomplished 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 reaching the Pittsburgh coal bed removed all doubts and filled us with intense respect for such records. The work in this county was not difficult 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 correlation and economic questions; there was no time for studies concerning matters of purely scientific interest. So intent were we in consideration 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, corrected 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 the field he found everything so simple that he was astonished that any one should have been perplexed and still more astonished that mistakes were