IOWA ACADEMY OP SCIENCE 
16; 
In the above table the first column of figures expresses the exact num- 
ber of pebbles found; the second, the percentages of all the pebbles; 
and the third, the percentages of the foreign material only. 
If in the above that which is local in character be excluded, all the 
remainder, are of a very resistant character, not a single specimen being 
found of the decomposed granite so common at the surface of the Kansan 
drift. The largest of the granites has a rough surface such as may be 
found in a granite of similar texture scaling under the action of frost. 
The almost complete absence of pink quartzites is also a notable fact 
wlien comparing the analysis with analyses of pebbles from the Kansan. 
The sizes of the largest pebbles are as follows : . 
Limestone — • 
4 xl%xl% inches. 
3%x3 x2 inches. 
31^x2 xli^ inches. 
3 xl 1/^x1 inches. 
3t4xl%xlt4 inches. 
2 xlt^xl inches. 
Granite — • 
3t^x3 xl% inches. 
3t4x3t4x2 inches. 
3 x2t4x2 inches. 
2%xl%x2 inches. 
2%x2 XIV 2 inches. 
2%xlt4xl% inches. 
Greenstone — 
41^x3 x2 inches. 
3 x3 X % inches. 
3 x2t4xl% inches. 
314x31^x2% inches. 
2t4x2 xlt4 inches. 
2%xl%xl inches. 
Quartz — ■ 
4 x2i4xl% inches. 
3 x2%xlt4 inches. 
Itixltixl inches. 
.114x1 X % inches. 
1 X %x % inches. 
114x %x % inches. 
Pink Quartzite — 
ly^xlViX % inches. 
CARBONIFEROUS. 
The bottom of the well is on a hard flat rock, which is undoubtedly 
a carboniferous, stratum in place, and presumably the source of many 
of the limestone pebbles found in the gravel. 
WATER. 
The character of the water obtained through the gravel bears evidence 
of the presence of partially decomposed vegetation (xVftonian). The 
water is so charged with free ammonia that the quantity of this ammonia 
was not determined. The albumenoid ammonia present was found to be 
thirty-two hundredths of a part per million. 
*The analysis was made by Professor C. J. Holmes. 
