The appearance at certain points of the series of stratified deposits of red sandstones and other rocks coloured by the peroxide of iron, in regions where the older formations contain comparatively few red beds, is a fact observed in many countries; and in some cases these red deposits are associated with rocks of more neutral tints, whose colours appear to be due to chemical changes which have affected portions of the red sediment. These phænomena, though often noticed, scarcely seem to be thoroughly understood either in reference to their causes or to the inferences which may be drawn from them. In the present paper I propose to state some facts in the geology of Nova Scotia which appear to be connected with the first appearance of red strata in that country, and which may perhaps admit of a more general application; and also to notice some changes now taking place in recent sedimentary deposits, which may explain the occurrence of occasional grey, greenish and white beds in formations whose prevailing colour is red. In Nova Scotia, red conglomerates, sandstones and clays predominate for the first time in the lower part of the carboniferous system ; and it is to this lower carboniferous series chiefly that the following remarks are intended to apply, though red beds continue to prevail in the newer carboniferous deposits and also in an overlying formation of red sandstone. The red colouring matter, which is the peroxide of iron, is in a very fine state of division
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