“STATE GEOLOGIST. 351 
In order to illustrate, first, the relation between tensile and crushing 
strength, second, the strength of neat and sand mortar, and, third, the 
relation between water and air hardening, the following results obtained 
by Tetmayer are given, representing the average strengths of 16 Swiss 
Portland cements : 
re ae Z : eG 
Time of hardening. Kind of mortar. EE oe 2 E Se S2 ue e 
S) En Ss) a 
MB CLAN Saari sont ee aires ss neat cement in water 479 5,754 | 12.01 
De) (0 NAS Reems eae ey do do 552 8,108 | 14.69 
SARA VSie. Mon cn ree ne do do ' 593 9,699 | 16.36 
MOcdayst do do 589 | 12,547 | 21.31 
SOOTUAY Sw emake nee. do do 633 14,346 | 22.67 
La GaVis ees: ee. 1 cement : 3 sand on water 293 3,033 | 10.35 
DST aySi Meee do do 312 4,014 | 10.79 
SANA Sareea enter do do 462 4,970 | 10.75 
DOsdaysue cee esl do do 520 5,859 | 11.27 
3105) CES 5 omer ara oe do do 604 6,319 | 10.46 
pe ee 1 cement :3 sand} in air 314 2,979 9.49 
SRG AVS Hct c tt suareiant teats do do 418 3,935 9.41 
SARC AV Silos feet ae do do 452 4,450 9.85 
POR VSise tacts Sve oes do do 508 4,605 9.06 
RG Chk eee do do. 621 5,143 | 8.28 
CONSTANCY OF VOLUME. 
_ Portland cements are liable to the following changes in volume: 
1. Increase in volume when hardening in water. 
2. Decrease in volume when hardening in air. 
3. Change in volume due to changes in temperature. 
4. Decided and irregular increase in volume due to abnormal con- 
ditions. 
1. It has been found in extensive tests made by Dr. Schumann that 
of eight cement mortars, 1:3, hardening in water, all showed an increase 
in volume. Expressed in terms of the linear expansion for a test piece 
To cm. long, the average increase in length was, after 7 days, 0.0123 per 
cent., aiter 4 weeks 0.0051 per cent., after 13 weeks 0.0025 per cent., 
after 26 weeks 0.0029, after 52 weeks 0.0052, after 2 years 0.0016 per cent. 
