Ch. XIII.] THE INCLINED POSITIONS OF STRATA. 263 



This example shows that it is not probable that these fan- 

 shaped strata were deposited in horizontal layers : but if they 

 were formed on inclined planes (the lowest being at the 

 greatest angle, and each deposit becoming more horizontal by 

 a greater accumulation at the lower part, according to the 

 laws of gravity), then there would be no occasion to call in 

 the aid of any movement, to account for the position of these 

 and similar formations. 



But can sedimentary depositions take place on inclined 

 planes, in beds parallel thereto ? are they not always accu- 

 mulated in horizontal layers, exhibiting truncated edges next 

 the fundamental inclined surface ? This is supposed to be 

 the mode of formation in most cases ; but it is admitted, even 

 by the advocates of an original horizontality, that it is very 

 possible for the former condition to have occasionally ob- 

 tained. Thus, as already stated, Lyell endeavours to account 

 for the inclined laminae between horizontal layers in the 

 crag, and in various schistose rocks. And the same author, 

 when contemplating the irregularly curved and diagonal 

 structure of the calcareous grit on each side of the pass near 

 Palagonia, in Sicily, remarks, " that it is somewhat difficult 

 to conceive in what manner this arrangement of the layers 

 was occasioned; but we may, perhaps, suppose it to have 

 arisen from the throwing down of calcareous sand and vol- 

 canic matter, upon steep slanting banks at the bottom of the 

 sea ; in which case they might have accumulated, at various 

 angles, of between 30 and 50, as may be frequently seen 

 in the sections of volcanic cones in Ischia and elsewhere. 

 The denuding power of the waves may then have cut off the 

 upper portion of these banks, so that nearly horizontal layers 

 may have been superimposed unconformably ; after which, 

 another bank may have been formed in a similar manner as 

 the first." * It is not necessary to pause here, to comment 

 on the probability of such a mode of formation ; it is suffi- 



* Principles of Geology, vol. iii. p. 72. 



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