REPORT OF THE DIRECTOR I9O4 



21 



main exceptions to the extreme flatness are low swells with a 

 northeast-southwest direction (the direction of the glacial flow) 

 and small sandy mounds of morainal origin. The swells or 

 ridges are glacial drift and essentially drumlins. In Monroe 

 county they are typical drumlins, but westward they become 

 more and more subdued anc^quite disappear in Niagara county. 

 The genesis of this remarkable plane is clear so far as its main 

 elements are involved. The underlying rock is Medina, mostly 

 shales but with resistant sandstone beds. The plane was de- 

 veloped by differential weathering in preglacial time. The in- 

 vading ice sheet smoothed the rock surface by planing and fill- 

 ing. Subsequently the area was lake bottom under the shallow 

 waters of Lake Iroquois, and the work of leveling and smoothing 

 was completed by the spreading of the Iroquois sands and silts. 

 Thus three agencies contributed to the result: atmospheric 

 erosion served to outline the geographic features, and glacial and 

 lake agencies to smooth it. The relative work of glacial and non- 

 glacial agents is not closely apportioned but may be more closely de- 

 termined by fuller study. The description of the " Niagara- 

 Genesee prairie " will make an interesting chapter in the geologic 

 evolution of the State. 



Hydrology 



My predecessor entered into arrangement with Mr George W. 

 Rafter C.E. of Rochester, a distinguished hydraulic engineer and 

 author of treatises on water supply and distribution, for the prepara- 

 tion of a general report on the hydrology of this State in which the 

 subject should be treated in comprehensive form. The report was 

 duly rendered and the printing is proceeding with adequate rapidity. 



Economic geology 



Louisana Purchase Exposition. The field work in this section 

 has been largely devoted to the collection of materials intended for 

 exhibition at the Louisiana Purchase Exposition which is specially 

 considered under a subsequent chapter. 



Marble. Aside from this H. H. Hindshaw has made a 

 brief study of the marble quarries in and about Gouverneur, St 

 Lawrence co., looking to the further development of these in- 

 terests in that region. He has reported that in the present op- 

 erations much useful material is being overlooked and there are 



