IOWA ACADEMY OF SCIENCES. 
31 
these exhumed boulders, as they occur at Graniteville, in Iron 
county, where they are known as “elephant rocks,” are shown 
in plate iv. 
The final stage of disintegration is the bed of sand with 
occasional decomposed pebbles of the original rock scattered 
through it. In the decomposition of granite the texture may 
remain in appearance as in the original rock, but upon excava- 
tion is found to be soft, incoherent sand. 
RECORD OF THE GRINNELL DEEP BORING. 
BY ARTHUR J. JONES. 
Work was begun on the deep well in October, 1892, but it 
was not completed until the following year. The ordinary churn 
drill was used and the hole was first drilled eight inches in diam- 
eter, but later the upper portion was enlarged to ten inches. 
The record has been more carefully kept than is usual in drill- 
ing such wells, but cannot be relied upon as absolutely exact. 
In many cases the fragments of the overlying stratum are 
mixed with that underneath, and the thickness of each forma- 
tion cannot be exactly determined. This renders the results 
only approximately correct, but it is believed that a fair degree 
of accuracy has been attained. 
The top of the well is at an elevation above the sea of 1,023 
feet. For 212 feet the drill passed through soil, loess and drift, 
but no record was kept. At this depth a hard limestone was 
encountered. The sample consists of small pieces of fine- 
grained limestone mixed with sand and gravel. A few pieces 
of coal and bituminous slate, which could hardly have been 
introduced from the surface, were also present. It had been 
thought that the coal measures probably extended as far as Grin- 
nell, but no positive evidence of this had been obtained prior to the 
sinking of this well. The gravel is the base of the lower till 
and the limestone evidently Saint Louis. At this point a strong 
flow of water was encountered. It rose to within 90 feet of the 
surface; higher than at any subsequent flow. The water was 
unfit for use, being almost yellow and strongly mineral; it had 
