44 [APPENDIX 



the former, should belong to the serpentine group, a useless shrub will 

 often be the resulting growth. 



Equally as perfect and marked are the phases presented on the valley 

 bottoms alone; passing through, the same transitions as above, and on 

 an examination of the sources from "which the soil has been derived, it 

 will be found that the mineral constituents of both sections presenting 

 those changes', will differ in a material degree. Take the upper terrace 

 - of any one of. our large valleys, and by following this to a lower terrace, 

 the first principal change occurring will be found near the junction of 

 the former, with the latter, and this as it recedes from the' former, will 

 be found productive of a widely different and greater variety of plants 

 than the hill-side or upper terrace preceding it, and the native nroduc- 

 tions of these, not unfrequently disappear entirely. ** 



Another feature equally interesting and instructive, is found iri transi 

 tions of the varieties of production on- the same line of valjey, which 

 has derived its soils from the same suite of rocks, this might easily be 

 mistaken for a change in the mineral constituents of such sbil, which is 

 not the case, but the modification of growths in this instance ae attribu 

 table to the more uniform and equal distribution and communication of 

 the material composing the soil, thus rendering its chemical constituents 

 better adapted to assimilation, and the consequent production of variety 

 as well as quality and quantity. 



The soils on the Bay San Francisco differ much on its eastern and 

 western sides ; both borders of the Bay present the tertiary series, but 

 both do not present the trapean rocks to the same degree of develop 

 ment ; this, then, of course, will cause a distinctive and marked differ 

 ence in the productive capabilities of either shore. It will be found 

 that in all the soils which have been .derived, in whole, or in part, from 

 rocks more recent than the tertiary group, that a more extensive and va 

 ried adaptation to agricultural purposes will be present ; this will be 

 particularly manifest in those sections where the tertiaries, containing 

 organic remains, enter somewhat largely into the -components of "the soil 

 produced from such sources. 



We often meet an extensive and even tract of country lying atothe 

 base of a range of hills of the character named above, which "are found 

 not to possess so high a degree of fertility as an adjoining section, yet 

 both have derived their soil from the same sources ; it becomes not only 

 interesting but important to ascertain the cause of such a discrepancy, 

 and an attentive examination will often point out a natural obstruction 

 of a mechanical nature wjhich has thus been the cause of the impover 

 ishment which may be present. In this case a barrier will often be 

 found among the foothills which has prevented the uniform distribution 

 of the ' disintegrated rocks above, rendering the plain within its line less 

 productive, rather than the introduction of any new agent, except, per 

 haps, that derived from the rocks forming that barrier, the amount of 

 which would be inconsiderable, compared to the mass of alluvium beyond. 



In illustration of this a single case only will be mentioned. On the 

 Valley- Santa Clara a few miles east of San Jose, the mountains are cap 

 ped with fossiliferous sandstone for miles in extent, north and south. 

 On examining the slopes of these hills and the broad ravines among 

 them, a rich and deep soil wafc found to cover the whole, and the ve'ge- 



