REVIEWS 627, 
crystals present in the dry plaster. This accords well with all the known 
facts in the case and is furthermore in line with Jameson’s observations 
on the setting of Portland cements. It explains some of the pecu- 
liarities of the behavior of retarders though in the matter of that vexed 
subject but little that is new is brought out. If the subject of the 
strength, and rapidity of set of the gypsum cements could have been 
gone into a little and illustrated by tensile strength and other tests it 
would have added greatly to the value of the book and have aided in 
defining the sort of situations in which these cements could be used to 
best advantage. In the form of hard white finish they now dominate 
the market so far as interior work is concerned but the advisability of 
using them for wall work in any general way is open as yet to some 
question. This is particularly true in view of the strength and cheap- 
ness of magnesian limes and the availability of non-sulphate cements. 
Dr. Grimsley’s report is a valuable one, particularly in its technical 
as distinguished from its geological phases. It will undoubtedly have 
a large influence on the gypsum industry of the state and is a credit to 
the vigorous Kansas Survey. H. F. Bain. 
American Cements. By Urian Cummincs. Pp. 299, 8vo. Rogers 
& Manson, Boston. 18098. 
In the rapid introduction of Portland cements in this country the 
importance and value of the Roman cements bid fair to be overlooked. 
At present there is what the author fittingly nominates a ‘‘craze”’ for 
quick setting, high testing cements, and the slower setting, cheaper 
grades are looked upon in many quarters as of very little value. Mr. 
Cummings’ long experience in the manufacture of cement and his wide 
interest in the subject admirably fit him to discuss it. In this little 
book he has gathered together much scattered information and has 
added very much from his own experience. His interpretations of 
the chemical processes involved in the making and the setting of 
cements will. doubtless arouse much opposition; particularly in his 
plea for the magnesian cements, but where so much is uncertain any 
hypothesis backed with such facts as Mr. Cummings marshals must 
necessarily receive careful attention. Taken as a whole the book is 
one of which no one interested in cements and the utilization of our 
limestones and shales, can afford to remain in ignorance. 
ie BAIN. 
