ANNIVERSARY ADDRESS OF THE PRESIDENT. XXXVU 



rents and small icebergs might deposit from time to time detrital 

 matter on a given rock-surface, but the first iceberg that succeeded, 

 large enough to reach down to that surface and grind over it, would 

 clear away the detritus previously deposited upon it, and smooth and 

 striate the rock itself. This might be repeated for a long period of 

 time, during which the process of striating the projecting surfaces 

 might be contemporaneous with that of permanent deposition at 

 points almost immediately contiguous, but at lower levels. Finally, 

 supposing a continued subsidence of the general area, the projecting 

 striated bosses would sink below the reach of the icebergs, and the 

 transport of matter still continuing, would become permanently 

 covered up. As the general area re-emerged it would be subject to 

 denudation, which might be expected to lay bare again some of the 

 striated rocks, and leave others permanently covered with detrital 

 matter as we now find them. 



Again, with reference to the combined operations of floating ice 

 and currents, it is not unworthy of remark that the former would 

 necessarily deposit least of its freight, ccsteris paribus, in its unim- 

 peded motion over deeper waters, and a greater part in its impeded 

 course over shallow bottoms. On the contrary, currents would de- 

 posit least on the shallow bottoms, where, cceteris paribus, their 

 velocity would be greatest, and most in the deeper waters ; and 

 moreover it would be in these deeper waters that the finer matter 

 would be deposited. Thus the existence of beds of finer and in many 

 cases stratified deposits, having more tumultuous deposits possibly 

 both above and below them, as in some parts of North America, does 

 not necessarily indicate a cessation in the more energetic action of 

 the forces of dispersion, but may merely indicate deposition in a 

 deeper sea. If also large angular blocks from distant sites should 

 be imbedded in this mass of finer matter, we see an additional indi- 

 cation of a deep sea in which a floating iceberg would, perhaps at 

 distant intervals, drop a portion of its freight. 



There is also a consideration connected with the process of trans- 

 port by certain currents alone, which, with reference to our inferences 

 as to the succession of events, is of some importance. I have men- 

 tioned it in my memoir " On the Granitic Blocks of the South High- 

 lands of Scotland,'' which appears in the last Number of our Journal. 

 Currents attending waves produced by sudden elevations, greater or 

 less, are necessarily transitory, and each can only carry the ma- 

 terials it may transport to certain distances, depending, eceteris pari- 

 bus, on the magnitudes of the component individual masses, the large 

 blocks being carried but to small distances, and the smaller particles 

 to much greater distances. Thus the first wave would produce a 

 layer consisting of the larger blocks near their source, and of fine de- 

 tritus at the remoter distances. The second wave would produce a 

 similar effect, and would also carry the blocks of the first wave to a 

 somewhat greater distance, and so on for successive waves. The 

 effect, then, of a succession of similar waves would be the formation, 

 over the more remote parts of the area of deposition, of a bed of 

 finer matter, in the upper portion of which would exist blocks rounded 



