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of Liguria , have been referred, with a highdegree of probability, to adjacent islands.

In vain did M. de Luc a object that these •coincidences on the opposite sides of val-leys are not found universally ; the theory,he rejected, does not require that theyshould be: it requires only that two placesseparated by a valley, should be as similarto one another as they might reasonablyhave been expected to be, had no valleyintervened. Where the interval is large, achange may easily take place in the nature,thickness, or position of the strata, andfrom the unequal hardness and destructi-bility which we should naturally expect indifferent rocks, vallies often extend alongthe lines of junction.

In the Orkney Islands may be seen aprimitive rock similar to one found at thenearest point of Norway , in contact witha secondary rock similar to one found atthe nearest point in Scotland . Had theinterval of sea occurred in any other spot,the contact would have been concealed:the opposite coasts would not have been si-* Travels in the North of Europe , p. 10.

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