238 ANNUAL REPORT 
of a higher lime content than the more aluminous clay bases. Unfor- 
tunately these tests are not quite as complete as it was desired to have 
them. It was also intended to carry on these tests by adding to the 
cements a little more water than they require for complete hydration, 
say 25 per cent., placing the cement and water into a metal capsule and 
immersing the latter in water. The rise in temperature would then 
give the hydration value under conditions approaching the practical 
reaction. Time, however, did not permit of carrying out these tests. 
For purposes of comparison the hydration values of a number of stan- 
dard Portland cements are given, using 10 grams of the sample and 
TOO cc. of water. | 
Calories per Gram. 
INS ice Fe Bass a ae ay ine neti area eA St, 3.43 
SDs Ba aA TN Ree Sr Ant ge ee a A SS BRING Cos aie a 6.41 
Ean Heo ee ae tits ot MR OLA D EIT ane hema nok eee a eo 
7 ear ire RR a eA) Ree O NT EL eet A Mer WEVE ot bi Fae te 3.98 
Ls Seep PERE Ree Snr Th ana, anes er PEA La iia) Oyun 1.04 
In order to supplement the results of the preceding series in regard 
to the best practical formula for dry ground mixtures of clay and 
limestone,the following cements were prepared, using as a basis a silicious 
clay found on the campus of the Ohio State University, a drift deposit of 
the following composition : 
Per cents. 
No) Ub Gr2 Pap inar eres ote lel eA MEDS RI eRe SAN LSS ages fae do 68 .82 
Aluminarand sinontoxdG ener DER ria a Fae es eae ae 19.20 
Gal eruirts XV OG oe ee ae rao neater pe 2.69 
Macnesium oxide ge sie tater oe neo eee Rei tere eee 2.46 
The limestone was a Carboniferous stone from near Wellston, Ohio, 
of the composition: 
Per cents. 
Caleiumicarbonatern tye ieee enna eae eee 91.80 
Slice F oa ae ee Oa eT ee OA Re ier 3) (DZ 
ANikoaoannne), Bal ROY CHIC, os nnccsccccvccveersesceounon 3}. Gul 
These materials were mixed and ground together intimately in the 
dry condition in an iron ball-mill, containing flint pebbles. The time 
of grinding was four hours, and practically no residue was left on the 
IOO mesh sieve. 
The clinker, after burning to complete vitrification, was ground in 
the ball-mill to a powder, leaving no residue on the 100 mesh sieve. No 
gypsum was added to the cement. The results of the test were as 
follows: 
