STATE GEOLOGIST. 203 
The white crystalline matter, as well as the dark ground mass, can 
readily be observed in the accompanying micro section made by the 
Writer. | 
The large crystal seen is a fine specimen of the alite found in 
normal Portland cements. 
Fig. 23. A large crystal of ‘“‘Alite’” in Portland cement clinker (highly magnified). 
The Later Work of Richardson.—The most thorough microscopic 
study of Portland cement is represented by the recent work of Dr. Clifford 
Richardson,* in which this investigator made an exhaustive experimental 
series involving various combinations of the mineral constituents of 
cement. ‘Thus he arrives at the result that pure clinker consists of two 
distinct solid solutions, alite and celite, the first being tri-calcic aluminate 
dissolved in tri-calcic silicate, the second di-calcic aluminate dissolved in 
di-calcic silicate. These, though miscible in the molten state, are not so 
in the solid form. The limits of the proportions of alite and celite depend 
on the basicity and the ratio of silicate to aluminate and are roughly 3 to 
1 and 6 to 1. This contribution furnishes the most valuable evidence for 
the solid solution theory as yet produced, but confirmatory proof based on 
other physical chemical methods of attack, such as the study of cooling 
curves, is still necessary for the final acceptance of this view. 
THE STUDY OF SYNTHETIC COMPOUNDS. 
This line of work was begun early in the scientific history of Port- 
land cement. It might wéll be said that Vicat, in France, was the 
pioneer in this kind of experimental work on a scientific basis, followed by 
Rivot, Chatoney and Fremy. In Germany we find Heldt, Fuchs, Schott, 
*Address before the Association of Portland Cement Manufacturers, June 15th, 1904. 
