348 PROCEEDINGS OF THE GEOLOaiCAL SOCIETY. [JuilG 19, 



descended from the Southern Alps in Postpliocene times. The pre- 

 sent rivers have invariably excavated their courses in them ; and the 

 swell of the ocean, having a northerly direction, has connected the 

 more advanced portions together by forming a dam of sands, behind 

 which estuaries and lagoons of greater or less extent have been 

 formed, washing the western foot of those morainic accumulations 

 which have not advanced so far. The headlands are those portions 

 of the moraines in which the greatest number of large blocks are 

 enclosed; in fact they correspond generally with the central and 

 lateral moraines. 



At the same time a partial destruction of these headlands has 

 offered the means for their further protection by raising at their 

 base huge masses of rocks, which extend into the sea for a consider- 

 able distance, and against which the waves break furiously but in- 

 effectually; whilst the softer beds between them, which have not 

 this protecting talus, are, if not constantly, at least during the fre- 

 quent gales along this coast, quite unprotected from the fury of the 

 waves, and are much less able to withstand their destructive power. 



Some of the imbedded blocks are of enormous size, often larger 

 than the celebrated Pierre-a-bot in the Jara. One of the most 

 striking examples is the large block lying in front of the centre of 

 the Baldhead moraine, to which it owes, without doubt, in some 

 degree its preservation. This block, which consists of contorted 

 clay-slate with layers of quartz, is from 30 to 40 feet in diameter, 

 and covered on its summit with a luxuriant vegetation. 



It is instructive to observe the manner in which the huge blocks, 

 when washed from the cliffs, or fallen from above when any por- 

 tion of the latter has been undermined by the waves, are soon buried, 

 in many places, in the marine sand which the southerly swell brings 

 incessantly along with it. These blocks, if not too large, wiU very 

 often sink considerably during one tide, the sand below and around 

 them being washed away, whilst another tide covers them up en- 

 tirely with sand left behind. Thus it will often happen that their 

 angles remain quite sharp after their burial in the sand, and are 

 thus preserved from further abrasion. But the upper portions of 

 many of the larger blocks remain uncovered, and are thus ex- 

 posed to the fury of the waves for a considerable time ; but, owing to 

 their extreme hardness, their angles become less rounded than might 

 have been expected. Of course there are many blocks which have 

 not only their edges worn off, but present that perfectly smooth 

 appearance so peculiar to rocks lying in the tidal way. 



These recent marine accumulations, in which former glacier- de- 

 posits are imbedded in marine sands with marine mollusks and 

 other exuviae, lead me to offer the following observations sug- 

 gested by a contemplation of this phenomenon. 



There is no doubt that, at least in some portions of the west coast, 

 the land is sinking rapidly, a conclusion repeatedly forced upon me 

 in passing the remains of forests now standing below high-water- 

 mark. Should this western side sink about 800 feet more by further 

 geological changes, by far the greater portion of these moraines 



