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The slates in the canton of Claris, inter-esting to naturalists on account of thefishes with wliiqh they are impressed, havebeen observed to be alternately thick andthin: M. Wittenbach, at Berne, threw outto me a very ingenious hypothesis to ex-plain this singular fact: he supposed thethick slates formed by the ebb-tide, and thethin by the flood: in his opinion, then theseslates could be no other than strata.

4th. Two or more sets of parallel planessometimes occur in the same rock, so a$ tomeet perpendicularly or obliquely.

At Ilfracombe, nodules of limestone oc-cur in lines which form nearly a right anglewith the planes of the slate in which theyare contained : in the same neighbourhoodmay be seen parallel interrupted veins ofquartz disposed in echellon, which also crossthe planes of the strata. At HedingtonQuarries, near Oxford , and at Anthony Hill,near Bath, the laminae of the freestone areunconformable to the larger divisions. Mr.Townsend* mentions an appearance of the

* Townsend’s Moses, p. 200.

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