lyo The American Geologist. September, 1902 
elusions may not be able to make observations which confirm 
the theories during his lifetime. In such cases subsequent ob- 
servations made through many years by others will find the 
phenomena confirming the principles. The truths announced 
by the man of insight are often not accepted by slower men 
until this latter observational work is done. Many cases could 
be cited illustrating these statements. Darwin, in i860, knezv 
that life had existed 'that would fill in the great gaps in the 
very imperfect paleontological record. Since i860 all the 
grep.ter gaps have been filled by discovered fossils. Mende- 
leefT. when he saw the law of the periodic arrangements of the 
elements, knezv the elements to exist which would fill the gaps, 
but it took many }'ears of work by many men to find a part 
of them. During the past few years a half dozen or more 
of the vacant places have been occupied. Each geologist, each 
scientist, now as in the past, is just as right as he should be. 
The scientific sears will ever go far in advance and guide 
others, even as did the spiritual seers of old. 
The scope of these observations doubtless extends beyond 
geology. ^luch of what has been said is true of knowledge 
as a whole, not restricted to one subject. But I shall have 
accomplished my puropse if what I have said be true of geology ; 
for if mv conclusions be well founded, they furnish the basis 
upon which courses leading to degrees in professional geology 
should be laid out, and to methods of good geological work in 
the field and in the office. 
INFLUENCE OF COUNTRY-ROCK ON MINERAL 
VEINS. 
' By Walter Harvey Weed, Washington, D. C* 
Among the many causes of that perplexing feature of mine- 
exploitation, the unequal distribution of the ore, the influence 
of the country-rock upon the vein-contents has long been ac- 
cepted as an important factor in certan districts, but the gen- 
eral application of the theory has not been proved. It is now 
possible to obtain trustworthy data with which to test the 
theory, and either to comfirm or to overthrow this tim.e-honored 
tradition. By the searching methods of modern petrograpihy 
* From the Trans. Am. Inst. Min. Eng. 
