IOWA ACADEMY OP SCIENCES. 
43 
Comparing the Indianola clay with these, with the first it is 
at variance especiall^^ in silica, alurniwa, and oxide of iron. With 
the second it corresponds very well except in Al^ O3 and in hav- 
ing more water. But we could not call it a sandy clay. The 
upper layer contains a little sand, but the lower practically 
none. To the third there is no comparison. 
It seems then as these clays represent the three common 
classes of brick, that this clay at Indianola must represent a 
kind which though it may make, as it has proven itself to do, 
good common building brick, yet it may be adapted to other 
kinds of brick. 
The Stourbridge, England, clays, from which the world- 
famed fire brick are made, yield, by averaging the analyses of 
four different clays, the following proportion of materials: 
No. 1. 
Si02 r 64.95 
AI 2 22 92 
Peg O 3 1.90 
Ca O+Mg- 0..__ .64 
K 2 0+Na2 O .37 
H 2 O loss 9.60 
Total 100.38 
Woodbridge fire clay bed, New Jersey, also famous for its 
quality of refractory clays, as follows: 
No. 2. 
Si O 2 combined 
40.50 
Si O 2 tree (quartz sand) 
6.40 
46.90 
^3 
35.90 
35.90 
Ti 02 
1.30 
1.30 
K 2 0 +Na 2 0 
.44 
O3 
1.10 
1 54 
H 2 0 combined 
12.80 
H 2 0 hygroscopic 
1.50 
14.30 
Total 
Prom Trenton, New Jersey: 
99.94 
99.94 
No. 3. 
Si O 2 combined 
17.50 
Si O 2 free (quartz sand) 
56.80 
74.30 
AI 2 O 3 
18.11 
18.11 
K 2 O— 0 "i~Ca 0 
1.07 
1.07 
Pe 2 O 3 +H 2 0 
6.99 
6.99 
Total 
100.47 
100.47 
