8 SMITHSONIAN INSTITUTION 



which had to cross a belt or patch of the sedimentary Cambrian 

 rocks were able to cut valleys rapidly, producing vertical-walled 

 canyons. Most of these are picturesque, the best being Ausable Chasm, 

 annually visited by thousands of people. 



A second major objective was study of the Cambrian sequence in 

 northwestern Vermont. Conditions there contrast strongly with those 

 in the Adirondack area across Lake Champlain. The Green Moun- 

 tains and hills of Vermont belong to the Appalachian Mountain 

 system, hence the rocks are strongly folded and overthrust. In the 

 Adirondack Mountains marine waters first flooded the flanks of the 

 old land mass to deposit Upper Cambrian beds which still remain 

 as more or less horizontal layers. In Vermont, however, the Cam- 

 brian sequence begins with the much older Lower Cambrian, and 

 intensive folding and faulting have given both the landscape and the 

 outcrops quite a different aspect. The earth movements altered the 

 limestones and shales into marbles and slates, which in turn gave rise 

 to one of Vermont's chief industries. 



The third major objective of the summer's work was study of the 

 Lower Cambrian deposits in the St. Lawrence valley. Outcrops begin 

 at Levis, directly opposite Quebec City, and extend intermittently 

 along the river for more than 200 miles, as very peculiar occurrences. 

 The rocks are limestones like those in the Straits of Belle Isle, Labra- 

 dor, but occur here only as boulders in limestone conglomerate. Out- 

 crops of such bedded rock are unknown along this vast stretch of 

 the river. Why and how these deposits came into existence is an 

 unsolved geological problem even though studied for about 100 years. 



Some of the limestone pebbles yield excellent fossils, but collect- 

 ing is difficult because both the pebbles and matrix are composed of 

 limestone so that both disintegrate simultaneously. Fossiliferous peb- 

 bles may be seen but, since they are not on the edge of the rock mass, 

 cannot be broken out. 



Near the tip of Gaspe Peninsula Cambrian strata have been found 

 in two small areas. These occurrences are intensely folded strata, 

 a continuation of the Appalachian system, and show thereby that the 

 seaways extended the great distance from central Alabama. Perce on 

 the tip of the Gaspe Peninsula is one of the most attractive places in 

 the world. Vertical cliff's of red, cream, and gray rocks, grassy slopes, 

 forested mountains, fish-drying racks, attractive homes, fishing boats, 

 and the sea combine to produce a beautiful picture. For years an 

 artist colony has tried to put some of this beauty on canvas, and 

 travelers are rejoiced by spending a few days at Perce. 



