46 PROCEEDINGS OF THE CALIFORNIA 



carried there, there must have been eight or ten feet of water over the surface, 

 and as the place is at present from ten to fifteen feet above the level of the 

 ocean, a rise of twenty-five or thirty feet must have taken place at this spot 

 since the animal was washed there. 



Another locality at which evidence of the gradual elevation of the land can 

 be obtained is found to the west of Black Point, where abundant remains of 

 our present bay shells are found at a considerable elevation above the level of 

 the sea ; aud, were not the surface of the country, particularly the lower levels, 

 so completely covered in by the drifting sands, no doubt many analogous deposits 

 could be found. To the south and west of the Mission, and in all the lower 

 levels between there and the range of hills overlooking the Puerta Suelo, the 

 surface is 'covered by these recent post tertiary deposits, through which the 

 older rocks protrude in many places as isolated masses, the recent argillaceous 

 sandstone being deposited in nearly horizontal strata around their base. These 

 sandstones have given rise, by their decomposition, to the extensive surfaces of 

 yellow sandy loam seen between the Mission and the Ocean House. I think the 

 highest of these beds does not attain a greater elevation than one hundred feet 

 above the present level of the ocean. 



More recent evidence of the gradual elevation of the land is furnished by the 

 holes made by the marine worms in the rocks on the shores of the bay, many 

 of these holes being found at elevations which the highest tides do not at pres- 

 ent reach. 



On the age of these deposits it is useless at present to speculate. All that we 

 know for certain is, that geologically speaking, they are recent ; but whether it 

 is five hundred, or five thousand, or fifty thousand years since the present site 

 of Mountain Lake was on a level with the ocean, our present data do not ena- 

 ble us to form an opinion. All that the facts prove is that this portion of the 

 continent is being gradually raised en masse. 



From observations I have made on the main range of the Sierra, I am 

 inclined to think that this process of gradual elevation is not confined to the 

 land bordering the sea coast, but extends far into the interior. The undisturbed 

 position of the post tertiary strata on the western slope of the Sierra, would 

 indicate that the same process of gradual elevation must have been going on 

 for hundreds of thousands of years, so that the original beach of the earlier 

 post tertiary ocean is now at an elevation of four or five thousand feet above 

 the present level of the sea. Should subsequent observations confirm the truth 

 of this supposition, this country would afford a more striking example of the 

 action of existing causes in modifying the surface of the earth, than is to be 

 found in any other portion of the globe. It is desirable that some means should 

 be taken to ascertain and record accurately the present relative level of the sea 

 and land, as, after a few years, such a determination might furnish some very 

 useful geological data. I have no doubt that it will be found that every shock 

 of an earthquake is accompanied by an elevation of the land. 



San Francisco, July 6th, 1 863. 



