GEOLOGY. 349 



from those farther up the valley ; but the theory that the water 

 deserts one well, to flow out of another of equal or higher 

 elevation, is not sound. There is very little difference of ele- 

 vation, perhaps ten feet, between San Jose and Alviso ; and 

 the wells near the latter place throw their water about five 

 feet higher above the surface than do those of the former. 

 One cause of the failure of the wells may be the filling up of 

 the pipes. From many of them great quantities of sand, 

 gravel, and stones half a foot in diameter, have been thrown 

 up ; and if a large stone should happen to lodge crosswise in 

 the pipe, the other smaller stones and gravel might soon stop it 

 up entirely, or break the force of the current so that the water 

 could not rise to the top. In many cases the pipe has not 

 been driven down to the foundation ; and the water, whirling 

 round at the bottom of the pipe, has torn away the earth and 

 made an excavation, thus preparing the way for a caving in 

 of the ground, and filling up of the well. 



Artesian wells have also been sunk in San Francisco, Oak- 

 land, Petaluma, Stockton, Fresno County, San Felipe, in 

 Montery County, the Colonia rancho in Ventura County, the 

 Los Angeles plain, San Bernardino, Kern, and Tulare Counties. 

 At San Felipe, a gaspipe with a steel point was driven down 

 with a mallet, until it reached a stratum of artesian water, which 

 now flows up in a constant stream. Some of the San Fran- 

 cisco artesian wells raise their water nearly to the surface, and 

 it must be pumped up for use. At San Diego an immense 

 supply of water has been reached by an artesian auger, but 

 does not come quite to the surface. San Bernardino County 

 has 100 artesian wells. 



278. Palaeontology. It is a general rule, that the animals 

 of former geological eras, in any given district, appear to have 

 been the gigantic ancestors of those of the present time. Thus, 

 the kangaroo and emu of Australia, found in no other part of 

 the world, were preceded by gigantic kangaroos and emus, 

 whose fossil remains are found in New Holland only. So, too, 



