376 The American Geologist. December, i897 
foot line and will be referred to as the lower conglomerate. 
All differences noted between the two are satisfactorily ex- 
plained b}' the fact that the upper conglomerate lies in imme- 
diate contact with the parent ledge, while the lower one 
represents the limit of the conglomeratic accumulation as it 
merges into the sandstones; the upper is thoroughly saturated 
with ferric oxide, while the lower contains more of the car- 
bonates; the upper has been more ett'ectually drained of the 
destructive alteration reagents which permeate the waters of 
such great reservoirs as sandstone strata become, while the 
lower has been more completely within their reach, so that its 
pebbles and boulders show both more extensive disintegration 
and a greater variety of secondary products. The cause of 
this difference between the upper and lower conglomerates at 
Taylor's Falls is still more strongly enforced by a comparison 
with that below Franconia, alreadj' described. In this latter 
exposure almost every boulder is well advanced toward the 
last stages of decay. Some of them are little more than an 
earthy compact mass — all now left of a once fresh lustre-mot- 
tled diabase, as is shown by the alternating blotches of green, 
gray and brown still to be seen upon the broken fragments. 
Still there is no evidence of an}"^ considerable time break be- 
tween these cf)nglomerates ; and the differences of surround- 
ing conditions due chiefly to their position, are believed to 
constitute the most potent cause of their variation. 
All boulders of the conglomerates are of the same petrologic 
character as the eruptive rocks now, or at one time, in place 
in the vicinity. No specimen of any rock belonging outside 
of this group of diabases was found among them. 
The conglomerate at Taylor's Falls belongs stratigraphicall3' 
to the lower part of the Franconia sandstone member of the 
Basal Sandstone series, and extends downward into the next 
underlying member, the Dresbach sandstone. The diabase 
conglomerate at St. Croix Falls belongs to the lower shales 
member, and that before noted in Sec. 1, T. 33 N., R. 19 W., 
apparently belongs to the St. Lawrence ft)rmation. 
Thus the conglomerates as a whole, do not belong to an}" 
siiigle member or formation, but are accumulations, resulting 
from special surroundings, which may, and no doubt do, occur 
at all horizons from the first one laid upon the Keweenawan 
