264 Address before the Association of American Geologists. 
The remarkable fertilizing power of green sand, first discov- 
ered in this country, has raised another question in agricul 
tural chemistry, of great practical interest, concerning which, 
there is not so much of an opposition, as of an unsettled state of 
opinion. The question is, which of the ingredients of this sab- 
stance produce the fertilization. All will agree, probably, that 
the potassa found in some green sand, acts an important part. But 
if this is the only ingredient, then the green sands of New Eng- 
land and old England, will be of no agricultural valne, as they are 
destitute of potassa: But others suppose that the. iron exerts a 
favorable influence ; and others, that the minutely divided state 
of the silica is jebicntatates asit seems to be in the Bergmehl, 
which is-also useful in agriculture. But I have time only to ex- 
press the confident expectation; that some of the gentlemen we 
hear me, will, ere many years, clear up this subject. 
~ Had not these subjects been so intimately connected with sev- 
eral of the state surveys, they might scem irrelevant on this occa 
sion. I return, therefore, to one more appropriately geological. 
But little has yet been published respecting the. anticlinal atid 
synclinal axes and their correspondent systems of strata in our 
country ; although I doubt not that numerous facts on the subject 
are in the note-books of our geologists, in respect to the particu- 
lar sections of country which they have examined. But this 1s 
one of those subjects upon which, as upon diluvial action, gene 
ral results, applicable to the whole country, can be made out’ 
after long examination ; it is one, therefore, peculiarly proper for 
such an association as I now wildeese ;—and I predict, that when 
the facts from different parts of this continent are collated and 
compared, it will be found that we have some of the most fe 
markable and magnificent systems of elevation and depression 
on the globe. There is no small reason to believe, indeed, that 
on the western side of this continent, from Cape Hora to the 
tic Ocean, one vast anticlinal axis exists, along the 
crest of the Andes ai the Rocky Mountains. Subordinate and 
_ Perhaps g systems of strata will undoubtedly be found 
long this extended line ; but this appears to be the great con 
tolling and probably the ‘most. recent uplift on the continent. 
The occurrence of voleanie vents along the whole line, W 
probabl 7 e th at the form has b upheaved at a later epoch thaa 
