418 
ELEMENTS OF GEOLOGY. 
was a growth of coral which was afterwards turned into crys¬ 
talline limestone, and parts of it, apparently by the action of 
sulphuric acid, into gypsum. In s})ite of continued sinking, 
amounting to several thousand feet, the sea might in time 
have been rendered shallow by the growth of coral, had 
not its conversion into land or swampy ground been accel¬ 
erated by the pouring in of sand and the advance of the 
delta accompanied with such fluviatile and brackish-water 
formations as are common in lagoons. 
The amount to which the bed of the sea sank down in or¬ 
der to allow of the formation of so vast a thickness of rock 
of sedimentary and organic origin is expressed by the total 
thickness of the Carboniferous strata, including the coal- 
measures, No. 1, and the rocks which underlie them, No. 2, 
Fig. 447. 
After the strata No. 2 had been elaborated, the conditions 
proper to a great delta exclusively prevailed, the subsidence 
Fig. 447. 
Diagram showing the curvature and supposed denudation of the Carboniferous 
strata in Nova Scotia. 
A. Anticlinal axis of Minudie. B. Synclinal of Shoulie River. 1. Coal-measures. 
2. Lower Carboniferous. 
still continuing so that one forest after another grew and 
was submerged until their under-clays with roots, and usual¬ 
ly seams of coal, were left at more than eighty distinct lev¬ 
els. Here and there, also, deposits bearing testimony to the 
existence of fresh or brackish-water lagoons, tilled with cal- 
careo-bituminous mud, were formed. In these beds {h and 
Fig. 439, p. 410) are found fresh-water bivalves or mussels 
allied to Anodon, though not identical with that or any liv¬ 
ing genus, and called Naiadites carhonarhis by Dawson. 
They are associated with small entomostracous crustaceans 
of the genus Cythere, and scales of small fishes. Occasional¬ 
ly some of the calamite brakes and forests of SigillariaB and 
Oonifer 80 were exposed in the flood season, or sometimes, 
perhaps, by slight elevatory movements to the denuding ac¬ 
tion of the river or the sea. 
In order to interpret the great coast section exposed to 
view on the shores of the Bay of Fundy, the student must, 
