STATE GEOLOGIST. _ 905 
ing. He also blended 8 equivalents of lime, 1 of potash and 4 of 
alumina, obtaining a more thoroughly vitrified mass, which, when pow- 
dered, hardened strongly in water, and heated but slightly. 
Fremy produced aluminates of the composition : 
RCAOAO,, ACAQANI On, CaOvVAil Ong 
_which hardened in water almost instantly. When mixed with sand, 
these aluminates became almost stone-like in character. Fremy thought 
the higher the aluminates were burnt the more hydraulic they were. Hence, 
he advised the burning of Portland cements to as high a temperature as 
possible, so as to fuse the aluminates and obtain the benefit of their 
maximum hydraulicity. 
Michaelis fused a mass of the formula 3CaOAl,O, in a gas flame 
fed with oxygen, and found the powder to harden exceedingly well. The 
hardened mass was attacked neither by carbon dioxide nor water. 
A mixture of 3CaOAl,O, thus fused and powdered set at once, but 
softened slowly under water. V. Lieven confirms the hydraulic activity 
of aluminates, but denies that they contribute to the permanent hard- 
ness of cements, since, according to him, they decompose into aluminum 
hydroxide, calcium hydroxide and calcium carbonate. The products on 
first hardening are: 
CaOAl,0,6H,O; 2CaOAl,O,5H,0; 3CaOAl,O,6H,0. 
Winkler also experimented with lime and ferric oxide, producing a 
mixture of eight equivalents of lime, one equivalent of potash and four 
equivalents of ferric oxide. ‘This resulted after burning in a _ black, 
slightly clinkered mass, whose powder heated strongly in water and be- 
came friable. Heldt burnt together one equivalent of ferric oxide with 
eight equivalents of burnt marble, and obtained a vitrified mass, which 
when powdered and made up with water heated but slightly, and soon 
broke down to calcium carbonate and ferric oxide. 
Michaelis was not at first successful in producing a fused or vitrified 
mass of calcium and iron, owing to a reduction of the oxide. In an 
oxidizing flame he obtained the compounds 3CaOFe,O, and 3CaO2Fe,O, 
as fused bodies, which when powdered were red or dark brown in color. 
Made up with water the 3CaOFe,O, body heated appreciably, the 
3CaO2Fe,O, compound did not. In air they became tolerably hard, in 
water they decomposed. 
In regard to the function of magnesia, the earlier investigators dis- 
agree most decidedly. Fuchs produced a good cement of great hard- 
ness from talc; Rivot and Chatoney claim that magnesia behaves an- 
alogously to lime, hardening in water like the calcium compounds, but 
do not advise the use of magnesia, owing to its slowness of hydration, 
