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5 . If the theory of Mr. Playfair weretrue, curvature should never be found inthose strata that are horizontal, whereashorizontal strata are often curved.

6. The conformity of different strata isanother circumstance fatal to this hypo-thesis. There is no species of rock in whichthe curves are more frequent or more fan-tastical than grey wacke slate ; this rock, weknow, in many instances, alternates with con-glomerate, the pebbles of which are disposedin such a manner, that it would be impossi-ble for them to remain an instant in theplace which they occupy, if the cementwhich connects them together were to be-come soft. The conglomerate, therefore,and consequently the slate which alternateswith .it, could not have been elevated,till after its consolidation. If, then, as theHuttonians say, it was not consolidated tillafter it was curved ; neither was it elevatedtill after it was curved: in other words, theeffect preceded the cause.

In regard to the supposition of Sir Jamesf 4