Crosby.] 
124 
[May 21, 
TABLE II. 
GRAVEL. 
SAND. 
FLOUR. 
CLAY. 
1. Mount Hope, upper till. 
26.53 
21.33 
42.13 
10.01 
2. Skinner Hill, lower till. 
24 66 
20.66 
48.31 
6.84 
3. Parker Hill, lower till. 
14.41 
20.09 
50.18 
14.68 
4. “ “ upper till. 
28.80 
16.90 
42.10 
11.00 
5. East Boston, lower till. 
27.90 
13.70 
47.76 
10.14 
6. “ “ upper till. 
29.10 
14.70 
41.81 
14.69 
7. Milton Hill, upper till. 
26.25 
18.80 
50.12 
5.68 
8. Convent Hill, lower till. 
24.50 
17.82 
46 39 
11.16 
9. <£ “ upper till. 
24.41 
19.13 
43.55 
13 46 
10. Mount Bowdoin, lower till. 
26.46 
17.04 
43.03 
12.92 
11. “ “ upper till. 
23.93 
20.54 
40.18 
15.18 
12 Ten Farm Hill, upper till. 
25.30 
24.93 
36.57 
13.44 
13. Green Hill, lower till. 
23.20 
17.28 
43.90 
15.27 
14. Long Island, lower till. 
16.72 
36.94 
38.03 
8.22 
15. Nut Island, lower till. 
20.73 
11.09 
52.49 
15.69 
16. Corey Hill, lower till. 
35.48 
21.28 
35.23 
8.41 
Average. 
24.90 
19.51 
43.86 
11.67 
The interest of the analyses evidently centers in the proportions 
of rock-flour and clay, the one surprisingly large and the other 
surprisingly small. Pure clay, instead of being the most abun- 
dant, is seen to be the least abundant constituent of the till ; and 
the main part of what appears to be clay is simply rock-flour, or 
quartz and other minerals which have been ground to an almost 
impalpable fineness. Our first problem appears thus to find an easy 
solution, for when the till is assorted or modified the stratified sand 
and gravel, it would seem, must certainly and greatly exceed the 
bedded clays. But before finally accepting this conclusion it will 
be best to observe what becomes of the rock-flour. The most cas- 
ual examination shows that it does not remain principally with the 
sand. Therefore it must in nature, as in the analyses, go with, 
and augment the volume of, the clay ; and analyses of the brick 
clays of this vicinity will be presented in the following pages show- 
