INTRODUCTORY. 29] 
of the origin of the gravels, those practically engaged in working them had 
arrived at much more correct conclusions in regard to some of the important 
points involved. It is for the satisfaction, then, of both practical and scien- 
tific men, that the following discussion is entered upon; and it is hoped 
that at least it may have the result of causing, in some localities, a more 
careful and systematic observation of some of the facts than has been hitherto 
customary. 
By consulting the Appendix to this volume,* it will be seen that after 
writing out his very voluminous notes on the region examined by him, which 
have been already presented in a condensed form in a previous chapter, Mr. 
Goodyear furnished a supplementary paper, containing a discussion of some 
of the difficult points presented by the gravels of the Sierra Nevada. This 
paper has been printed in full in the Appendix, and it should be read with 
care by all interested in these geological problems. This abstract, prepared by 
Mr. Goodyear, has been printed not only as an act of justice to him, but also 
as throwing light on some points of importance. The writer’s opinions differ 
very considerably from those of Mr. Goodyear in regard to certain of the 
main questions involved, as those who take the pains to read the present 
chapter and Appendix B will readily perceive. The writer’s views, how- 
ever, are based on a long-continued series of investigations in every part of 
the gravel region, while Mr. Goodyear was naturally most strongly impressed 
by the phenomena which had been specially well exhibited in the district to 
which his work was mainly limited. 
It should not be forgotten that the entire body of views and opinions in 
regard to the mode of occurrence of the gravel is something which has long 
been under discussion among the various members of the corps of the Geo- 
logical Survey, carried on under the writer’s direction. All that is definitely 
known to science in regard to these matters comes from the work of that 
survey, as has already been clearly set forth in a previous chapter, where in- 
deed credit has been given to those of the practical miners whose views have 
in some important respects been much more nearly consonant with the truth 
than those of any of the scientific men who had visited the region pre- 
viously to the appearance of the Geology of California, Vol. I. 
What has here been stated in regard to the theories of the gravel, and ine 
divergencies of opinion in regard to vital points connected therewith, will 
be better understood after a perusal of the following section, in which the 
* See further on, Appendix B. 
