STATE, GEOLOGIST. 83 
to northern Michigan and Canada. Besides this the ice, owing to its 
enormous weight, exerted great pressure on the surface and compacted it. 
As is to be expected, the glacial or drift clays of Ohio are a 
heterogenous material of extreme irregularity of composition, containing 
bowlders of all sizes, sandy at one place and again full of limestone 
pebbles, besides many other extreme variations. We can reduce our 
treatment of the glacial clays to the statement that as such they are unfit 
’ for consideration as cement materials. 
The only way by which they can be made workable by nature is 
redeposition, which may give rise to local deposits of great value for 
cement. making. The bowlder clay must be washed by rivers or creeks 
into lakes where the fine mineral matter is deposited, giving rise to 
fine grained clays of more or less uniform composition. If the compo- 
sition is suitable for the manufacture of Portland cement, having the 
proper silica-alumina ratio and being low in magnesia, such a clay 1s of 
great value and should be carefully explored. Its importance can, how- 
ever, be only local, since it was deposited in a lake in a given locality 
under favorable conditions. All these clays have a tendency to be 
irregular in composition and must be watched carefully in winning them. 
The table on page 84 gives analyses of several glacial clays: 
Columbus drift clay analyzed by the rational method gave the follow- 
ing result : 
Per cents. 
@lavesulbtance msm ien amc sated anuarnn Wa atiemtli 5 ei Seo OO 
VT ATCA eesuaer crore ver ahatareele Nittods Jensen eh Alege) starts weiky sWealsnte Gules eens AAD () 
Reltdsiathieuimattertcamn tes cer deem serrate lode eater. 20.18 
Calcirummcanooma tes writ lela Voverdla lee aia cee sleteinn ave 4.02 
- SANDSTONE AND SAND, 
There may be cases in which the prevailing conditions demand the 
addition of silica as such to the Portland cement mixture and it may 
hence become necessary to look for a silicious material. It is evident that 
such a material must be fine grained and easy to grind if it is to become 
available for this purpose. The most suitable sandstone has already been 
mentioned as being an accessory of Bedford shale, namely Berea grit. 
Of course this stone is not everywhere suitable, it being in places very 
hard and difficult to grind, while again it may be coarse grained and 
irregular in composition. ‘The fitness of a stone for cement purposes 
must be determined for each local deposit. The stone is frequently made 
more easily reducible by being heated in a vertical shaft furnace built 
exactly like a limekiln, and quenched while hot by a stream of cold water. 
It would not be necessary to raise the temperature very high, a good red 
heat being ample to accomplish the desired result. 
Though sandstone may not be available, sand is found in so many 
localities that a satisfactory kind will be ‘accessible almost every where | It. 
is evident that the sands also differ greatly in physical and chemical 
