IOWA ACADEMY OP SCIENCES. 43 



Comparing the Indianola clay with these, with the first it is 

 at variance especially in silica, alumina, and oxide of iron. With 

 the second it corresponds very well except in AU O^ 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. 



SiOj-. --- 64.95 



Alj O3 ---- 22.92 



Fe^ O3.... -. - 1.90 



Ca O+Mg O --- .64 



Kj O+Na^ O 37 



Hj OI0SS-- --.- - 9.60 



Total -- 100.38 



Woodbridge fire clay bed, New Jersey, also famous for its 

 quality of refractory clays, as follows: 



No. 2. 



SiOj combined 40.50 



Si 02 free (quartz sand) 6.40 46.90 



Alj O3 35.90 35.90 



TiOj -_. 1.30 1.30 



KjO+NaaO.- 44 



Fej O3- 1.10 154 



H2 O combined .--- 12.80 



Hj O hygroscopic 1.50 14.30 



T.otal 99.94 99.94 



From Trenton, New Jersey: 



No. 3. 



SiO, combined 17.50 



Si O2 free (quartz sand) 56.80 74.30 



AljOg-... 18.11 18.11 



K^O+Na^O+CaO 1.07 1.07 



Fe^Og+H^O 6.99 6.99 



Total 100.47 100.47 



