Characteristic crystals obtained by 

 the microscopic test from calcium 

 oxide ignited at a red heat. 



Fig. 8.— Characteristic plume-like formations 

 of crystals obtained from sintered 

 lime in Portland cement. 



Fig. 15.— Photograph of sound and disintegrated com- 

 mercial Portland cement clinkers. (1) Char- 

 acteristic sound, weathered, stationary kiln 

 clinker split open to show its homogeneous 

 and perfectly sintered condition; (2) piece 

 of raw-meal brick which had almost escaped 

 the fire; the particles of ground limestone 

 were held together by the cohesion of the 

 dehydrated, compressed clay; this shows one 

 possible source of the carbon-dioxide in com- 

 mercial cements; (3) characteristic disinte- 

 grated product of weathered, underburned, 

 stationary, kiln clinker. 



