42 
IOWA ACADEMY OF SCIENCES. 
The sample above this as follows: 
Si 02-_. 67.85 
AI2 03-j~F62 O3 _ 20 45 
CaO 1.19 
Mn O. ______ ___ trace 
K2 O ___ trace 
Loss dried at 100°___ 3.47 
Loss by ignition 7.12 
Total 100.08 
It will be seen that in each there is a large per cent, of silica 
and alumina. The upper containing more free silica, conse- 
quently gave a higher per cent of silica and alumina, but con- 
tained a considerably smaller per cent, of hygroscopic moisture, 
The higher loss by ignition in the upper stratum being due 
doubtless, to a larger amount of organic matter near the sur- 
face. Lime was present in the upper stratum in appreciable 
quantity, and iron in small quantity in each. A trace of man- 
ganese oxide in the upper stratum. 
From Crossley’s “Table of Analyses of Clays” for common 
brick we take three average samples, which are as follows : 
Common brick clay: 
Si O2 ___ ____ 49.44 
AI2 03__ 34.26 
Fc 2 O3 7.74 
Ca O 1.48 
Mg 0._ 5.14 
Water and loss 1.94 
Total 100.00 
Sandy clay: 
Si02 66.68 
AI2 O3.' ___ _._ 26.08 
Fe2 O3 1.26 
Mg O trace 
CaO .84 
Water and loss 5.14 
Total 100.00 
Marl. — London “Malms.” 
Si O2+AI2 O3 ..._ 43.00 
Fe2 O3. 3.00 
CaO 46.50 
Mg O 3.50 
Water-. 4.00 
Total 100.00 
