152 THE CAEBONIFEROUS SYSTEM. 



thick beds of limestone and gypsum. The mode of formation of this 

 last rock I shall not now notice, as better opportunities will occur 

 hereafter. Respecting the limestones, I may remark that they are 

 marine deposits, formed in an open sea tenanted by various kinds of 

 shell-fish, etc., the remains of which still exist in the limestone. They 

 are principally bivalves of a family (the Brachiopoda) once very abun- 

 dant, but in the modern world represented by very few species ; and 

 the most abundant shell of this kind in these limestones is the Pro- 

 ductus Cora, a finely striated species, having one valve very convex 

 externally, and the other very concave. It is found in rocks of the 

 same age in Great Britain. There is also a nautilus, nearly resembling 

 in form the nautilus of recent tropical seas, but smaller in size ; and 

 there are numerous fragments of Crinoids, a tribe of creatures allied to 

 modern star-fishes, but furnished with a stem by which they were 

 attached to the bottom, while their radiating arms extended on all sides 

 in quest of prey. These limestones must have been formed in a sea 

 whose waves lashed the slopes of the Cobequid Mountains and ground 

 up the pebbles of old rocks which now form conglomerates on their 

 flanks, while beds of shells were accumulating in its more quiet depths. 

 Its northern boundary may have been the Silurian and metamorphic 

 rocks of Lower Canada and Labrador. 



The limestones above described dip to the southward ; and if we 

 proceed across the country in the direction of their strike, we find them 

 again with the same fossils on the Hebert River near Minudie ; and in 

 the opposite or eastern direction, at several places nearly in a line 

 between the Napan and Pugwash Harbour on the shore of Northumber- 

 land Strait, where the limestone with its characteristic marine fossils is 

 largely developed. Leaving in the meantime the rocks that lie to the 

 northward of and under this limestone, we may take that part of it 

 which appears near Minudie as the base of the Joggins section. Fol- 

 lowing its direction across from Hebert River to the Joggins coast, we 

 find there that it is overlaid conformably by a great series of sandstones 

 and shales, which we shall now proceed to describe, just as we should 

 see them if walking along the coast ; and if this process should seem at 

 all tedious to the reader, I beg him to remember that this finely 

 exposed series of beds furnishes the key which will enable us to under- 

 stand the whole structure of the Coal formation of Nova Scotia and 

 New Brunswick ; and further, that this key to facts so important both 

 in geology and in reference to the economical value of the coal-fields, 

 is now for the first time brought in a complete form before the general 

 reader. 



Commencing at Seaman's Brook in Mill Cove, and taking Logan's 



