Iriassic Traps of Nova Scotia, etc. — Marsters. 141 
stone also dips in the same direction and at the same an- 
gle. Hence it results that the abrupt termination of the 
southeastern edge of the trappean area, gives a monoclinal 
form to the valley on the south of the mountain. The depth 
of the valley has undoubtedly been increased, by the erosion 
of the sandstones, a fact of which there is abundant evidence. 
This agent was probably the chief means in reducing also the 
thickness of the trap on the brow of the mountain. The sand- 
stone area, which is severed into two distinct parts by the in- 
terruption of Minas basin and Avon river, extends on the 
southwest through Kings, Annapolis and Digby counties. In 
the eastern part of Horton township it overlies highly inclined 
and partially metamorphosed slates and shales of Carbonifer- 
ous age. The Carboniferous series is admirably exposed on 
the Avon river and is generally known as the "Horton Bluff" 
series.^ The eastern part of the Triassic area can be traced in 
irregular patches along the shores of Minas basin and Cobe- 
quid bay as far east as Onslow and Truro, where it was ob- 
served to rest unconformably upon limestones and shales ex- 
hibited in the hills of Osnlow and along North river. 
It attains its greatest width (18 miles) in Kings county, and 
gradually decreases towards each extremity. 
The general geological features of this trappean ridge sug- 
gest that it was formed by a true submarine volcanic erup- 
tion. This conclusion is strengthened by the fact that the 
formation is composed of two definite layers, the lower strat- 
um being composed of scoriae and volcanic ashes, the upper 
stratum of much denser, firmer and often columnar trap, a 
phenomenon which is known to exist in almost all volcanic 
regions. 
In comparing this deposit with similar ones in the United 
States, I notice a striking resemblance between them. In one 
or two particulars, however, some different features occur 
which are worthy of note. The Triassic traps of the eastern 
states have received considerable attention from Prof. W. M. 
Davis, who considers all trappean deposits Avhose upper strat- 
um presents an amygdaloidal or vesicular structure as evi- 
dence of an "overflow," which has cooled without subjection 
to overlying pressure. Hence wherever the deposit has at- 
'^ The "Horton Bluff" series has been well described by Sir Win. 
Dawson in his "Acadian Geologj'," p. 92 and p. 252. 
