626 REVIEWS 
but brief notes on the gypsum of other states and countries and a full 
discussion of the mining and milling processes. The body of the work 
is by Dr. Grimsley while Professor Bailey contributes a welcome chapter 
dealing with the chemistry of the subject. 
In 1897 Kansas produced 50,045 tons of gypsum which had a value 
of $252,811. It was a little behind Iowa in production and ahead in 
values; the difference being in the large proportion of the Iowa prod- 
uct sold as land plaster. Aside from these two states Michigan and 
New York are the main producers. The Kansas gypsum is found in 
three fields; the Northern or Blue Rapids area mainly in Washington 
and Marshall counties, the central or Gypsum City area of Salina, 
Dickinson, and Marion counties, and the southern or Medicine Lodge 
area in Comanche and Barber (misprinted Barton on map) counties. 
The beds occur in the Permian of Prosser’s classification and the 
deposits include the original rock deposits and the derived gypsum 
earths which are of recent origin. These gypsum earths are the dis- 
tinctive beds of the Kansas-Oklahoma district and are thought to be 
marsh deposits deriving their peculiarities from the secondary deposi- 
tion of gypsum in clays. ‘They are used in the production of gypsum 
cements and are mined by ordinary surface methods. The rock 
gypsum is won by underground mining on a room and pillar system, 
of which a more detailed account would have been valuable, and are 
used in the production of plaster of Paris and other products. 
The Kansas milling practice does not seem to differ from that of 
other districts especially, though the Stedman disintegrator has been 
introduced and a cooling air blast is used at one point to elevate the 
calcined plaster. Here as elsewhere grinding is in the main done by 
stones and it seems peculiar, in view of the great progress of recent 
years in fine grinding machinery, that the numerous experiments in 
the direction of cheaper and more expeditious grinding have never 
borne fruit inthe gypsum industries. Burning is done in the ordinary 
Marsh calcining kettle. It would seem that in the case of the gypsum. 
earths at least the rotary furnaces now so much used could be applied 
to advantage. 
In the discussion of the set of the plaster Dr. Grimsley has con- 
tributed some highly interesting and valuable microscopic studies in 
which he shows, in brief, that the strength of the set plaster depends. 
upon the formation of a network or felt of fine lath-shaped crystals and 
that the quickening agents in this setting process are the few small. 
