88 Remarks on a Tertiary Deposit 



the reasons which make this conclusion apparent. It will be 

 sufficient to say that the want of horizontality in the smaller 

 strata is due to the force of the current, and the greater divi- 

 sions are caused by an alteration in the direction of the stream, 

 which, before it would deposit any new matter, would carry 

 away the lighter superficial particles, and wear down to a 

 smooth surface all inequalities. The material of the rock 

 would appear, at first sight, to be a coarse-grained sandstone. I 

 should call it a calcareous sandstone. Under the microscope 

 it is found to consist of small particles of shells, worn by at- 

 trition into thin scales and small grains of quartzose sand. 

 It is freely acted upon by weak acids, and on a quali- 

 tative analysis showed a large proportion of silica, lime and 

 magnesia (carbonates), with small proportions of sesquioxide 

 of iron and sulphate of lime, but no appreciable quantity of 

 phosphates nor organic matter. It would not be difficult to 

 show that the formation was deposed in deep water, perhaps 

 at some considerable distance from the coast ; for anything 

 but a slow-moving large body of water out of the influence of 

 land would certainly carry down larger fragments of shells 

 than what are here seen. From the great attrition the parti- 

 cles have been subjected to, one can gather that they were 

 carried a long distance. The place where the deposit is seen 

 to best advantage is in a small bay on the southern side of 

 Cape Lannes, which with its projecting reef forms the termi- 

 nation of Guichen Bay on the south. Here the rocks are 

 seen in bold sections, over fifty feet in thickness. This little 

 bay is very deep, so that the water washes the foot of the 

 cliffs nearly all round. In some places the wearing of the 

 surf has undermined the cliffs and caused them to fall in, or 

 the spray has eaten into their soft, friable texture, giving 

 them a wild jagged outline. These features, united with 

 irregular cross stratification, the dark hue of the stone, 

 the heaps of ruins which are scattered about, and the boiling 

 of the surf as it breaks heavily against the rocks, even on the 

 calmest day, would make a grand and sublime scene, were it on 

 .a somewhat larger scale. However, even as it is, it is wild and 

 desolate, and the little verdure which the Mesembryanthemum 

 give as they creep down the surface of the rock, or hang 

 swaying in the wind, tends little to soften the savage aspect 

 of the place. There are, as I have before stated, no fossils, 

 but the summit of each cliff is topped by a stratum of com- 

 pact limestone, horizontally deposed, and lying unconforma- 

 bly. This, I presume, is the relic of the last coast action 



