290 RESUME AND THEORETICAL DISCUSSION. 
which should be a trustworthy guide to the miner in determining before- 
hand where work could be carried on, at what cost, and also with what profit. 
The problems presented are too difficult and complicated, in most cases at 
least, to be settled without actual experiment. Still, it is true that a good 
deal of assistance could be rendered, in the way especially of preventing 
wasteful expenditures, if a systematic examination of a sufficiently detailed 
character could be made of the gravel region, accompanied by a careful in- 
spection of all that was doing in each important district and a full record of 
everything observed. Such an investigation should, however, have been 
begun long ago, for already a great deal of valuable information has been 
lost forever, there being no one on the spot sufficiently intelligent or inter- 
ested in the matter to seize the opportunities presented for examination, and 
which can never recur after the right moment has passed, and the locality 
gone to ruin or been abandoned. As a preliminary to any such work, how- 
ever, an accurate contour-line map, on a very large scale, would be absolutely 
necessary, while the natural difficulties of such a survey are so great that it 
could not be made without a large expenditure. . 
It is hardly necessary to say that the work of any geological survey, to be 
of practical value, must be continuous and never-ending. The conditions of 
every region of metalliferous or other deposits of economical value are con- 
stantly altering as exploitation goes on. Old mines are worked out, new 
ones are discovered, new processes are invented, other more prolific regions 
opened, forbidding competition on the part of the poorer ones, prices rise and 
fall as the supply increases or diminishes: all these changes make the devel- 
opment of the mining resources of any region something to be always looked 
after by the Government, if looked after at all. And it is in accordance with 
such views as these that in civilized countries, where mining inspection exists 
at all, its task is a never-ceasing one, its execution, moreover, being intrusted 
to the competent hands of men specially and thoroughly educated for it. 
The present chapter, then, must be looked upon as an attempt to throw 
light on some of the scientific problems presented by the auriferous gravels 
of California, rather than as a practical guide to the miner in his work. 
Not that it may not interest those actually engaged in hydraulic mining. 
On the contrary, it appears that the miners themselves are, in many in- 
stances, greatly exercised in their minds by the curious phenomena with 
which they are brought in contact; and it has already been noticed that, 
while so-called scientific observers were utterly mistaken in their views 
