AMETCIOAN GEOLOGY DECADE OF 1850-1859. 4()9 



It has been generally assumed that such sandstones were originally formed by 

 mechanical agencies, the material being supposed to have gradually accumulated 

 from the grinding down of previously existing quartzose rocks. The facts collected, 

 however, seem rather to point to chemical than mechanical causes. * * * AVe 

 can hardly understand how such an amount of quartzose sand could have been accu- 

 mulated without its containing at the same time a considerable quantity of detritus, 

 which could be recognized as having come from the destruction of the schistose, 

 feldspath, and trappean rocks, which make up the larger portion of the Azoic series 

 wherever it has been examined. The uniform size of the grains of which the sand- 

 stone is composed and the tendency to the development of crystalline facets in them 

 are additional facts winch suggest the idea of chemical precipitation rather than of 

 mechanical accumulation. « 



In 1850 Prof. Edward Hitchcock was appointed State geologist of 

 Vermont, and continued to serve until 1860, at which time he submitted 

 his final report, which appeared in 1861 in the form of two quarto vol- 

 umes of 982 pages, accompanied by a colored geolog-- 



Hitchcock's . ■ , . fc& 



Geology of Vermont, ical map of. the State, two maps showing the terraces 

 and beaches, and 35 plates ol scenery, fossils, sections, 

 etc. Hiteheoek was assisted in the work by his sons, Edward Hitch- 

 eock, jr., and C. H. Hitchcock, and by Albert D.. Hager, in whose 

 charge was placed the final publication of the work. 



The main objects of the survey, as outlined in the introduction, were 

 first, to gain such a knowledge of the solid rocks of the State as to be 

 able to delineate them upon maps and sections; second, to study the 

 loose deposits lying upon the solid rocks and trace "out the changes 

 which the surface of the State had undergone; third, to collect, arrange, 

 and name specimens of rocks, minerals, and fossils from every part of 

 the State for the State cabinet; fourth, to obtain a full collection, for 

 the same cabinet, of specimens valuable from an economic standpoint; 

 and fifth, to identify the metamorphosed rocks of the State with those 

 which had not been thus changed. 



The systematic geology was in immediate charge of Professor 

 Hitchcock, though aided by C. B. Adams, Zadock Thompson, A. P. 

 Hager, and C. H. Hitchcock. The economic geology was in charge 

 of Hager, and the chemistry, of C. H. Hitchcock. The Rev. S. K. 

 Hall aided in the preparation of a report on the northern part of the 

 State and its agricultural possibilities. The paleontological work was 

 done by James Hall, and the paleobotanical by Lesquereux. Hitch- 

 cock recognized at this date that each rock formation was character- 

 ized by its peculiar group of fossils not found in any other; so that a 

 paleontologist, on seeing a specimen, could usualty tell from which of 



«The explanation of this error lies in the fact that the grains of which this sand- 

 stone is made up have been cemented by a secondary deposition of interstitial 

 silica, so deposited as to convert each granule into a more or less perfect crystal, of 

 which the original sand grain forms the nucleus. It is a case of secondary growth 

 and enlargement, a phenomenon now well known to every petrographer, but 

 undreamed of at the time of Whitney's writing. 



