186 ANNUAL REPORT 
burnt cement, 3 for over-burning without vitrification, 4 for vitrification. 
The composition of the stone (layer No. 12) was as follows: 
Per Cents. 
SITCOMS TESLA Se ar etae a eee re edlas iets ese eet y ANGE 19.64 
aU bb be GnU 0: Rome aerraMien, era r re Stealv aan HN Srey yuh Ut DU 792 
UNeh gKenrops¢ (0 (elaine ane eye revel aeons ee Meal casa ea SRAM Ug 2.38 
Calcium: carbonates tsrl oii. aslo) SiSen Arann emma 30.72 
Magnesium carbonatem emai hier iiceiemn i is Coan lena 39.10 
95.36 
The ordinates represent the breaking weights of rectangular parallel- 
opipeds, 2 inches by 2 inches by 8 inches, the pressure being applied at 
Fig. 19. Gilmore’s curves, showing double maxima and minima in strengths of 
cements by variation in burning temperature. 
the middle. Curve No. 1 represents 1 volume cement to 2 volumes sand, 
age 95 days; No. 2, neat cement, 95 days; No. 3, neat cement, 60 days; 
No. 4, 1 volume cement to 1 volume sand, 60 days. 
The same results are recorded by Feichtinger as having been 
obtained by Gaetschenberger with dolomitic marl from near Heidelberg. 
Summary of the Results, —Summarizing the results in regard to 
the burning of Roman cements, we can make the¢following statements: 
Ist. For Roman cements, high in lime, approaching the tri-calcium 
silicate and low in magnesia, best burning temeprature is 1000° C. Such 
stone can be made into Portland cement by vitrification. This cannot be 
