rrport of the progress of the geolo- 

 gical survey of* thfj state of virgi- 

 nia, for the year 1s36. 



By William B. Rogers, 



Professor of Natural Philosophy in the University of 

 Virginia. 



I b8£T leave to make ilie following report of the 

 proi^re.ss of the geological survey of the state, 

 (luring the [)ast year. 



Pro|)er assistants having been appointed, as 

 provided in the law, the active investigations in 

 the field were beffun about the middle of April, 

 and were continued without interruption until the 

 beginning of November. Durinii this time and 

 nearly up to the present date, whilst not myself 

 enijjaifed in the task of exploration, t!"-j chemical 

 researches connected with the survey have been 

 steadily progressing under n)y immediate and 

 constant superintendence. 



In aid of the field operations, and as an impor- 

 tant preliminary to the correct delineation of geo- 

 logical details upon the state map, the work of 

 taking accurate copies of the county maps was 

 bstrun earl)' in the season, and has progressed so 

 far as that at the present time more than fifty of 

 these maps are ready for the uses of the survey. 



In the course of the geological investigations of 

 the season, upwards of twenty boxes of speci- 

 mens were collected, illustrating the structure and 

 economical resources of the various districts visit- 

 ed, and lurnishing materials for analytical exami- 

 nation. 



In the prosecution of the work, each of the fol- 

 lowing regions was more or less the theatre of re- 

 search. 



1st. The peninsula of the Potomac and Rappa- 

 hannock rivers. 



2d. The counties bordering on the Rappahan- 

 nock to the south. 



3d. The bituminous coal fields of Henrico, 

 Goochland, Chesterfield and Powhatan counties. 



4th. A portion of what is called the '"gold re<rion" 

 in the counties of Fauquier, Spottsvlvania, Cul- 

 peper, Louisa, Orange, Goochland, Fluvanna and 

 Buckingham. 



5th. A transverse belt of coimtry extending 

 westward from the neitrhborhood of Fredericks- 

 burg, to the vicinity of Moorfieid, in Hardy coun- 

 6th. The northern counties of the valley, fi'om 

 the Potomac, to the neighborhood of L\iray aru! 

 Newmarket, together with a portion of the adja- 

 cent mountain district to the west. 



7th. The counties of Washington, Wythe, 

 Smyth. Montgomery and Grayson, in the south- 

 west. 



In most of the districts above enumerated, the 

 investigations were conducted in the manner of a 

 reconnoissance, with the view of establishing a 

 basis for future specific and accurate research, and 

 it is important to bear in mind, that from the diver- 

 sified features of our geology, and the almost total 

 absence of anv knowledge of it from previous in- 



VoL. IV— 90 



vesligation, such preliminary stirveys in each dis- 

 trict become indispensable to the successtid and 

 rapid prosecution ol'the minute inquiries which are 

 to constitute the chief value of the survey. But 

 while lor the most part, the operations of the p;ist 

 yenr were of the general character heredescribcil, 

 in some districts the observations were carried 

 into minute detail, and in all of them a great 

 number of ficts were gathered, calculated to illus- 

 trate their geoloixical structure, and the nature and 

 extent of their mineral resources. 

 ■ But as the exhibuion ot details at present, would 

 obviously be incompatible with the design of "the, 

 annual reports upon the progress of the survey" 

 contemplaied in the law — they will be reserved for 

 incorporation in the final report — in the mean- 

 while, having the benefit of a revision, with the 

 additional lights acfjuired in the prosecution of the 

 work. 



In the first of the regions above indicated, the 

 observations were very numerous and minute. 

 Nearly all the important exposures, illustrating 

 thegeologvand nfmeral resources of ihe peninsula, 

 were carefully examined ; the strata observed in 

 each, being; noted, and specimens retained for illus- 

 tration and chemical research. The boundaries of 

 the two divisions of the tertiary, the eocene and 

 ineiocene, were determined with all needful accu- 

 racy upon the Potomac and Rappahannock, and 

 were approximately settled as to iuteruiediate 

 points. 



The disposition and nature of the beds compos- 

 ing the meincene in this portion of the state, were 

 found to be comfi)rrnaltle with those of the penin- 

 sula of the James and York rivers, chiefly referred 

 to in the report of the reconnoissance published 

 last year. Here, as well as in that region, the 

 bluish marls were found low down in the series of 

 meiocene strata, and a thin band of ferruginous 

 rock or clay was generally observed to be inter- 

 posed between them and the diluvial sand and 

 (jravel. Indeed, so uniform is the position of this 

 layer, in relation to the marl, that its discovery at 

 any point ronald furnish grounds ftr the strong, if 

 not confident anticipation of finding marl beneath. 



A large proportion of the marl beds of the Neck, 

 containinor carbonate of lime in sufficient quantity 

 to prove available in airriculture, are of the descrip- 

 tion which has just been noticed; at the same 

 time stnita in which the shells are miuirled with 

 sand and clay of various shades of yellow and 

 brown, are not nnfrequent. A fi'agmenlary rock, 

 consisting of broken shells cemented by carbonate 

 of lime, sometimes partially crystallized, and white 

 pulvemlent or chalky marls are also found. 



Of these the most abundant, or blue marl, though 

 ol'ten presenting the appearance of great richness 

 from the numberof perfect shells which it contains, 

 has been found to be less charged with carbonate 

 of lime, than some of the other varieties. 



The mean of upwards of fifty specimens of this 

 description which have been analyzed in the coarse 

 of the season, is 36 per cent, of carbonate of lime ; 

 and in lew instances did the result rise as hich as 

 40 per cent., while the light colored rocky and 



