1848.] DAWSON ON COLOURING MATTER OF RED SANDSTONE. 25 



below the ocean. To explain the phsenomena, therefore, of the ap- 

 parent transport of boulders from a lower to a higher level, it is only 

 necessary to suppose that the land during its repeated elevations and 

 depressions was subjected to a slight angular motion, and the whole 

 difficulty is removed. Now, setting aside the case of Northern 

 Europe, where we know from actual measurements that such a move- 

 ment takes place, and the instances of earthquake elevation in which 

 it has also been supposed to occur, such a kind of motion seems more 

 probable than the elevation of whole continental masses in an exactly 

 vertical direction. To produce the latter, the elevating power must 

 act with equal intensity below every part of the surface, and everywhere 

 experience a uniform resistance ; or the one of these powers be every- 

 where exactly proportioned to the other ; neither of them supposi- 

 tions at all likely to be reahzed on a mass composed of such various 

 materials as the crust of the earth. 



May 31, 1848. 



H. Wedgwood, Esq. and T. Brown, Esq. were elected Fellows. 



The following communications were read : — 



1. 0)1 the Colouring Matter of Red Sandstones and of Greyish and 

 White Beds associated with them. By John William Dawson, Esq. 



[Communicated by Sir Charles Lyell, V.P.G.S.] 



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 phsenomena, though often no- 

 ticed, 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 occur- 

 rence of occasional grey, greenish and white beds in formations whose 

 prevailing colour is red. 



In Nova Scotia, red conglomerates, sandstones and clays predomi- 

 nate 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 forma- 

 tion of red sandstone. The red colouring matter, which is the per- 

 oxide of iron, is in a very fine state of division, having indeed rather 



