114 University Geological Survey of Kansas. 
for illustration. Patent number 291,508, of May, 1883, gives a 
mixture of plaster of Paris, glue, glycerin, sawdust, slacked lime. 
Patent number 446,604, of December, 1890, gives a mixture of 
beans, peas, lentils, slacked lime, carbonate of soda, and alkaline 
earth. Patent number 456,297, of March, 1891, gives a mixture 
of plaster of Paris, sawdust, slacked lime, sand, sugar, and car- 
bonate of soda. Patent number 453,743, of October, 1889, gives 
a mixture of glue, oil or fat, muriatic acid, and sulphuric acid. 
Patent number 393,002, of April, 1885, gives a mixture of plas- 
ter of Paris, paper pulp, flour pack, sawdust, fiber, salt, and cop- 
peras. Patent number 458,742, of March, 1890, gives a mixture 
of oil meal or flax-seed, an alkali, and properly treated portions 
of hoof, horn, orfeathers. Patent number 390,157, of February, 
1888, gives a mixture of plaster of Paris, glue, sawdust, Irish 
moss, molasses, tartaric acid, whiting, and sand. Patent num- 
ber 544,142, of March, 1895, gives a mixture of tankage of ren- 
dered fats. Patent number 558,435, of October, 1892, gives a 
mixture of plaster of Paris, furnace slag, slacked lime, hydraulic 
cement, flour of grain, and fiber. 
The exact influence of the retarder upon the plaster is not 
known, but it seems to hold the water and so hinder the rapid 
crystallization of the plaster. Whether this weakens the cement 
plaster or not is a disputed question among architects and plas- 
_ terers. 
It is very doubtful whether a good mineral or organic retarder 
will injure the plaster. The fact that it hinders the set or crys- 
tallization of the plaster would lead to the inference that the 
plaster would not be injured, for it it merely delays the time, and. 
the resulting crystal network would be as strong as though no re- 
tarder was there. Poor retarders, by their decay, would proba- 
bly weaken the plaster, but where used in small amounts the 
effect should not be very great. The safe method would be to 
use good retarders, which are not subject to decay, and to use 
them in small amounts. 
After the hot plaster passes from the kettle to the ground bin 
it remains about an hour to partially cool, and then it is raised 
to the second story. It is next bolted or screened in some way. 
