STATE GEOLOGIST. 129 
Finally a synthetic mixture, having the following composition, was 
prepared with the intention of closely imitating such a clay as is commonly 
found in the alluvial or glacial clays of the country, and as is likely to be 
tried as a source of silica and alumina in cement manufacture. . 
Per cent. 
Commercial washed kaolin ......... Paar hay Beads hs 50 
Held sparwlls 0-12 Ohmeshee re sme es ee 10 
eld siearelt2 OOO sie shine et cps eesc ret casa lentes 10 
PQ uanbzamlo O12 0 meshes circa seal. ce ce ad ayaa ede are io coess 10 
Quan lOU=SOcmmeshwe eles ae ie oi aeseeal Sere 10 
Oust ZAG O=4 Onmeshierew eects qatar centre ter cic mas ok Seas 10 
100 
This mixture would have on analysis a composition roughly as fol- 
4 
lows: 
Per cents. 
SiOMre nee ey tn arctan tira at sutine, vor Gens Meee 65.50 
NOME eee Ea anon as 24.00 
ECOG Sande eee ae nee a are yh ie 3.00 
ISCO ns eae See ee ee eles eee eee 7.50 
100.00 | 
Upon being heated with lime it showed, on analysis, a residue of 
31.36 per cent., 68.64 per cent. having been taken into solution. ‘The 
residue, calculated from the previous experiments, should be 30.72 per 
cent., which is a practical check on the previous work. 
The foregoing method has yet to be subjected to the wide test of 
practical application. Not until it is demonstrated that the clays 
which this method condemns, are also condemned after actual use as 
cement materials, and that clays which this method endorses as good, are 
actually found good in use, can it be treated as an established and valu- 
able thing. 
However, its claims to usefulness rest on broad and secure technical 
reasoning. Noone can successfully dispute that clays, which give up their 
silica most readily to the action of lime, are, other things being equal, the 
best for making cements. Neither can any one affirm that any other 
method yet proposed or used, has been successful in showing any close 
relation between the amount of sandy minerals in a clay and its value to 
the cement-maker. 
The clay must contain other sources of silica than that of kaolinite, 
if it is to be serviceable to the cement-maker, and, in addition, these 
sources must be such as will readily yield it up. The older methods have 
stopped after showing that the requisite silicate matter is present. This 
proposed method is designed to go one step farther, in showing not only 
9—S. G. Bull. 3. 
