Mr. C. Babbage on the Action of Ocean-currents. 69 



Ryan, are coarse conglomerates of granite, porphyry, &c., and 

 towards the middle of the section are schists with graptolites, which 

 latter, from the general southern dip of the strata and the frequent 

 absence of the axial arches, appear to overlie the former. The 

 graptolite-schists, however, are the equivalent of the graptolitic and 

 anthracitic schists of Dumfriesshire, Selkirkshire, and Peebleshire, 

 and are really lower in stratigraphical position than the conglo- 

 merates of Corswall Point and the conglomerates and limestone of 

 the south of Ayrshire, of which the Wrae limestone, with its asso- 

 ciated conglomerate, is the counterpart. The abnormal relative 

 position of the conglomerates and graptolite-schists on the western 

 coast of Wigtonshire is due, in the author's opinion, to an inversion 

 of the rock-masses, similar to the great inverted flexures of strata 

 seen in the Ardennes, the Eifel, the Appalachians, &c. This great 

 folding up of the Silurian strata has thrown them into axial folds 

 which have an E.N.E. strike, similar to that prevailing over the 

 north of Ireland, the south of Scotland, and even in Norway, and 

 must be due to some physical cause which has operated on a mag- 

 nificent scale. In the author's opinion, the granites of Cairnsmuir, 

 CrifFel, &c. have been protruded subsequently to the great move- 

 ments above alluded to, and have somewhat deranged the E.N.E. 

 strike. 



2. "On the action of Ocean -currents in the formation of the 

 Strata of the Earth." By C. Babbage, Esq., F.R.S. Communi- 

 cated by W. H. Fitton, M.D., F.R.S., F.G.S. 



In the first part of this paper the author traced out the laws 

 which regulate the distribution of very finely divided earthy matter, 

 borne outwards from river-mouths and sea-clifFs into the ocean- 

 currents, over extensive areas. The time that a particle of matter 

 requires to fall through a given distance in a resisting medium 

 depends — 



1st. On the specific gravity of the particle itself. 



2nd. On its greater or less magnitude. 



3rd. On its form. 



4th. On the law of the resistance of the medium through which 

 it falls. 



These several points were treated of by the author, who then 

 proceeded to show under what conditions certain finely triturated 

 substances, of given size and composition, suspended in a current 

 of a given velocity, would be deposited in a sea of a given depth. 

 He noticed also how the uniformity of a stratum might be interfered 

 with by the varying conditions both of the sediment and of the 

 sea-bottom. Altered relations between the specific gravity, the 

 shape, and the size of the particles, when duly adjusted, render 

 ocean-currents capable of either separating mixed substances, or of 

 combining together different substances. Hence endless combina- 

 tions arise from the variation of these conditions. 



Local elevations and depressions of the sea- bed, on which sedi- 

 ment brought from a distance is deposited, were pointed out as 

 probable causes of irregularities in stratified deposits, — giving origin. 



