276 _ Messrs. Jackson and Alger on the 
Unlike most other extensive formations of this rock, its breadth 
‘is altogether disproportionate to its length, not exceeding in any 
place three miles, and in some places, where it has been 
worn away into deep ravines on the seacoast, scarcely exceeding 
a hundredth part of its extent in the opposite direction, If 
averaged, probably the breadth of the whole mass of the North 
mountains, including Digby neck, will not be found to exceed, 
at most one thirtieth part of its whole length. From this 
circumstance, we may regard it rather in the light of an immense 
dyke, thrown up from beneath the sandstone through some vast 
and continuous rent, produced by the sudden eruptive upheaving 
of its strata, which allowed it to spread out laterally only to a very 
limited extent ; and if theory is to be admitted at all, we know 
not how the origin of such a singularly disproportioned mass can 
be accounted for in any other way. Its regularity of outline, its 
continuity, and especially its almost exact linear direction, are 
against the notion of its being the ejected matter of successive 
eruptions, and warrant the opinion we have above expressed as to 
its origin. It offers a very striking exception to the remark made 
by Professor Daubeny, though his ingenious reasoning is strictly 
applicable to it in other respects, that “ the more ancient volcanic 
rocks seem to form continuous strata, spreading more uniform- 
ly on every side over a large extent of country ;” which he 
says is the case with the basalt of the Giant’s Causeway, the 
toadstones of Derbyshire, the porphyries of Edinburgh, and the 
trachytes of Mont d’Or.* And we have reason to believe that, mm 
the progress of discovery, this remark, although once apparently 
true, will meet with similar exceptions in other countries. 
/ 
* See Professor Daubeny’s Description of Actiye and Extinct Volcanoes, 
page 407. 
