Mahyland Geological Survey 45 



first time identified tlie succeeding formations from this mountain west- 

 wai'd nearly to the summit of Dans Mountain. 



Ducatel's reports of Maryland considered mostly the topography of west- 

 ern Mainland and its economic rather than stratigraphic geology. The 

 report for 1840, published in 1841, gives a description of the physical 

 geography of Allegany (which then included Garrett) and Washington 

 counties together with some account of their geology. It contains a topo- 

 graphic map of western Maryland from South Mountain to the western 

 border, a " Geological profile of the Cumberland and National Roads " 

 and states that between Sideling Hill and Dans Mountain the prevailing 

 rocks are limestone, red sandstone, and slate. 



On the " Geological map of the Middle and Western States " accom- 

 panying Professor James HalFs report of the Fourth District of New 

 York, published in 1843, the southwestern continuation of certain New 

 York formations is shown across Pennsylvania, Maryland, and Virginia. 

 Pour different colors are used to represent those formations now referred 

 to the Devonian, all of which cross western Maryland, and the following 

 names and grouping are given in the legend: Helderberg limestones in- 

 cluding grits and sandstones, Hamilton group including Tully limestone 

 and Genesee slate, Portage and Chemung groups, and Old Eed Sandstone. 

 The outlines of the formations in Maryland are credited to the State 

 Geologist, Professor J. T. Ducatel. 



The (ieology of Pennsylvania, or Professor Henry D. Eogers' final 

 report, was finished in 1858 and in this work in addition to the Roman 

 numerals for the formations, appeared what has been called the trans- 

 cendental nomenclature of Rogers. He stated that " it became apparent 

 to the State Geologists of Virginia and Pennsylvania, Professor W. B. 

 Rogers and myself, that none of the existing systems of nomenclature — • 

 neither the imported Britisli ont's, nor the narrowly local geographical ones 

 of New York — were applicaMr to our strata."' The Paleozoic rocks 

 were di\i(k'(l into fifteen formations or series for which he used terms 

 significant of their relative age "'the words employed suggesting meta- 

 phorically the ditt'erent natural periods of the day." " In this elassifica- 



^ Geology of Pennsylvania, vol. i, Preface, p. vi. 

 "Ibid., p. vli. 



