6 



to collect and determine the fossils which they might be found to con- 

 tain. In thus ascertaining the relation of the several parts of the 

 Cambrian terranes to each other, and their distribution, a cruide would 



* t O 



be had also to the location of mineral deposits which the Cambrian 

 rocks might contain. 



INTRODUCTORY. 



THE STRUCTURE OF THE CAMBRIAN ROCKS IN CAPE BRETON, AND THEIR 

 CONTAINED FAUNAS. 



Knowledge of Since the survey of the Cambrian areas in Cape Breton was made 



f~* V\ .' 



system 13 * ^y Mr. Hugh Fletcher some twenty-five years ago, our knowledge of 

 extended. the Cambrian system in America has been greatly extended, notably 

 by the explorations of the United States Geological Survey, and 

 through the efforts of its present able director. Much also has been 

 done by the Canadian Survey, especially in the region of the Rocky 

 mountains, the valley of the St. Lawrence, and in Labrador. 



In the province of New Brunswick the structure and faunas of the 

 Cambrian rocks have been worked out by private effort, and from their 

 proximity to Cape Breton are most reliable for comparison with those 

 of that island. The series there also is so complete that it yields a 

 good standard of comparison for all the Atlantic coast Cambrian 

 deposits. 



Earlier survey After the exploratory work of the Canadicin Geological Survey had 

 Fletcher. been opened in Cape Breton, Mr. Fletcher, in 1874, began the study 

 of the areas where the Cambrian rocks are found, and continued his 

 work there for three years, when the further prosecution of the sur- 

 vey carried him beyond the Cambrian areas. 



In the progress of Mr. Fletcher's work in the Cambrian districts he 

 had found that the sediments of this age lie in several narrow valleys 

 inclosed between abrupt hills of Pre-Cambrian rocks, mostly crystal- 

 line or metamorphic ; and in one broader valley, that of the Mira 

 river. It M r as in the valley of this river that the fossils were found, 

 which determined the Cambrian age of the above mentioned rocks in 

 Cape Breton. 



The carefully delineated topographical details given by Mr. Fletcher 

 in his excellent maps, the record of the dips and strikes of the rocks, 

 of the nature of the sediments, and of the localities where fossils were 

 to be had, materially aided the writer in investigating the geology of 



