38 Murchisons Silurian System. 



and in the mass of rock on which the town itself is built, the 

 beds possess nearly all the characters of the sandstones in 

 the higher parts of the system, being thick-bedded, soft, of a 

 deep red colour, and traversed by innumerable lines of false 

 bedding, which often meet in wedge-like forms. 



" I may here remark, that whether considered in its central 

 or in its lower member there is no system of rocks which 

 occasionally offers greater difficulties for determining its real 

 laminae of deposit than the New Red Sandstone. Besides 

 the joints or fissures, the diagonal lines of false stratifica- 

 tion are sometimes so prevalent, that it is only by tracing at 

 wider intervals the true laminae of deposit, as marked by 

 herbage or moss, that we can correctly ascertain the real 

 dip of the strata. As these appearances sometimes re-occur 

 from top to bottom of cliffs two and three hundred feet in 

 height, and as the intervals between the true beds is often 

 fifteen or twenty feet, it at first sight does not seem easy to 

 assign an adequate cause for the accumulation of such a vast 

 number of interjacent laminae, parallel to each other in se- 

 parate wedges, yet divergent from the lines of true bedding. 

 Such appearances are to be found to a certain extent in 

 rocks of all ages, and however difficult it may be to explain 

 the precise method by which water can have deposited the 

 grains of sand in these positions, we have positive evidence 

 of precisely similar phenomena, not only in young tertiary 

 deposits like the crag, but also in those accumulations of the 

 modern era, which having been formed under the sea, have 

 subsequently been raised up, and occupy low cliffs along 

 certain parts of the coast of our island."* 



* " See description of a raised beach on the north coast of Devonshire, by the Rev. 

 Professor Sedgwick, and Mr. Murchison, Geol. Proceed, xi. No. 48. Mr. Lyell has 

 given an ingenious explanation of the manner in which these transverse laminae 

 may have been formed by water, in showing how similar inclined planes of sand 

 are accumulated by wind. Mr. De la Beche also throws light on the origin of 

 this false bedding, Theoret. Res. in Geol. p. 88." It appears to us unnecessary to 

 limit the cause of the phenomena alluded to, to the action of water alone ; why 

 might winds not also have been engaged in producing them as they are at present ? 

 The traveller on the Ganges and Bramaputra has frequent opportunities of ob- 

 serving the peculiar structure alluded to in sands of many miles in breadth on 

 either side of the streams. — Ed. 



