276 American Geologist. ^^y- i^<^^ 
The conclusion to which we are driven, by reasonable con- 
sideration of the facts that I have presented, is necessarily that 
throughout this gorge wells may be sunk through the clay or 
drift deposits, whatever they may be, and into the St. Peter 
sandstone, and that they will afford water of the best quality, 
which will in many places flow over the surface and which will 
in all cases rise at least to the level of the Mississippi river. 
The area of this belt amenable to such uses is about 1334 square 
miles. 
Artesian Water From the Bottom of the St. Peter Sandstone. 
I will call your attention now to the diagram (Fig. 4) and 
especially to No. 4 of that diagram, which represents a shale 
within the St. Peter sandstone. This shale is sometimes all in 
one bed and is from one to two or three feet thick, but accord- 
ing to the testimony of well-drillers it is sometimes separated 
into two or three thinner sheets and is then interlaminated 
with sand, the whole amounting to perhaps five feet. This 
shale bed serves as a confining stratum for waters under hy- 
drostatic pressure which are in the St. Peter sandstone below. 
In some places this shale is represented to be near the bottom 
of the St. Peter and in other places it is represented to be about 
thirty feet above.the bottom of the St. Peter sandstone. My at- 
tention was first called to the existence of this shale and its ac- 
tion upon the waters confined below it by the record of a deep 
well which I noticed and reported in 1882. It affords an over- 
flow of artesian water in the deep well at the Washburn C 
mill, so-called, situated near the river on the west side, oppo- 
site the falls of St. Anthony. The record states that below the 
clay or shale is a coarse white sand rock, from which water rises 
to the. surf ace from the depth of 183 feet. As the water here 
rises to the surface of the ground there is an indication that 
the stratum of clay is of cpnsiderable extent laterally. This 
shale bed is probably passed through by every drilled well that 
goes to that depth. In some cases it is distinctly noted in the 
record of deep wells, but in many cases it is not noted, the dril- 
lers having ignored it. In the West Hotel well this shale was 
met at a depth of 168 feet, and in the sand rock below it was 
found the first water at a depth of 178 feet. Shakopee lime- 
stone was then met at a further depth of 24 feet. In this well 
also this shale which gave the first water was disregarded. 
