Geologij of the St. Croix Dalles. — Berkey. 355 
numerous small streams in this area, the largest being util- 
ized for water power for several manufacturing establish- 
ments. Most of them originate in the springs issuing from 
the river blufPs and flow at once to the river, onl}^ a few rods 
away. Their erosion effects are not very pronounced in any 
single case, although the combined effect is to remove a com- 
paratively-large amount of rock material. Those streams 
which originate in the springs located in the drift hills, or 
in similar situation, have eroded quite extensive gorges 
and frequently exhibit exceptional exposures of the un- 
derlying sedimentary rocks. Several streams whose entire 
supply of water in dry seasons comes from the springs along 
their courses are in wet seasons the outlets of the lakes of 
the district. The most notable of these streams are: 
1. Rock creek, originating in the morainic lakes near the northeast 
corner of the area, and following a glacial valley to the river. 
2. Dresser creek, following the old glacial overflow plain from near 
Dresser Junction to the river. 
3. Brown creek, originating in the sloughs north of Colby lake and 
following a tortuous course to the river in Sec. 2, T. Si N., R. 19 W. 
4. Lawrence creek, situated in the western portion of the district, 
the most notable one, on account of the gorge it has cut through the 
sandstones at Franconia. During part of the year it is dry in a portion 
of its course, but the springs originating at the head of the gorge al- 
ways furnish a considerable flow of water in its lower course. Its ero- 
sion effects are entirely disproportionate to the present size of the 
stream. This creek is the natural drainage for many of the sloughs, 
which were once lakes of considerable size on the fiat till plain lying in 
the western part and even beyond the bounds of this district. It, no 
doubt, had a much greater volume of water at that time. The effect of 
this stream has been to cut a fine gorge from the river at Franconia 
along the line between sections 2 and 3 (jf T. 33 N., R. 19 W., for more 
than one-half milo in length and to a depth of from 150 to 200 feet be- 
low thf surrounding surface. No such erosion is elsewhere to be found 
outside the St. Croix gorge itself. 
Chaptek II. Glacial Geolor/i/. 
I. The (rlacial Drift. Most parts (»f the district are heav- 
ily covered with drift. The only portions lacking it entirely 
;tre the more prominent outcrop])ing ridges of igneous rocks. 
The parts most thickly covered are the preglacial valleys, and 
probably the tract now occupied by the moraines at the east- 
ern side of the district. Exact measurements are f»btainable 
in but few places. 
