REPORT OF THE DIRECTOR I QIC 95 



of the Adirondacks at the time of deposition. There is some ground 

 for this inference. Similarly in the actual highlands of Sweden, 

 land areas, already carved into hills and deep valleys, are believed 

 to have existed in Cambric time (4, p. 6). 



The nature of the surface on which the Poughquag sandstone 

 north of the Highlands of the Hudson was deposited is so little 

 exposed that we can cite it for comparison. 



Professor Hogbom states (4, p. 4) that at most of the contacts 

 between the Cambric and older rocks in Sweden, one finds the 

 bottom layers of the former resting on a weathered breccia of the 

 subjacent xA.rchean. The breccia turns into kaolinized gneiss which 

 continues to a depth of one or two meters. These relations are 

 paralleled at the " Noses " along the Mohawk where the Beekman- 

 town limestone rests on decomposed gneiss (5) but the general ex- 

 perience in New York is to find rather fresh Precambric rocks 

 beneath the Cambric, as if the advancing waves had swept the old 

 bedrock clean of the products of weathering. In Sweden one cur- 

 ious feature of these contacts remains far away from present 

 exposures of the Cambric strata. A few little, so-called " sandstone 

 dikes " have been found in crevices of the ancient gneisses. In 

 them Cambric brachiopods which serve to establish the age have 

 been detected. One of these on a high hill of gneiss, on an island 

 ofif the east coast of southern Sweden, not far from Vastervik, was 

 shown to us and excited much interest. It reminded the Americans 

 of the similar explanation suggested by Prof. J. E. Wolff for the 

 narrow Cambric quartzite in the crystalline limestone at Franklin 

 Furnace, N. J., (6) discovered by Mr F. L. Nason and believed by 

 him to be interbedded (7). 



The most recent scheme of classification of the Precambric 

 which has found favor in Sweden is in part the one suggested by 

 Professor Sederholm, the Director of the Geological Survey of Fin- 

 land, where, over a vast area, scarcely any other than Precambric 

 rocks appear, and where careful studies have been carried on in 

 later years. In part also it has been suggested by Professor Hog- 

 bom of Upsala. Beneath the Cambric strata we find the following 



(4, p. 2) : 



'Epijotnian dislocations 



Upper or Jotnian -< 



Jotn'ian 



Snbjotnian land surface denudation and 

 . igneous rocks 



