For gray concrete for any
purpose they use: Alum, 8.46; caustic soda, 0.28; whitening or chalk,
0.56; borax, 0.56; water, 90.14; total, 100.00. For floors or slabs _in
situ_ they add to cement, well mixed and incorporated with any required
proportion of agglomerate for a base, liquid composition of the following
proportions: Oxide of magnesia, 0.29; chloride of magnesia, 0.29;
carbonate of soda or alum, 4.74; water, 94.68; total, 100.00. Articles
manufactured by the invention are afterward wetted with chloride of
calcium and placed in a bath containing a solution of silicate of soda or
chloride of calcium. The strength of the chloride of calcium is equal to
about 20 deg. specific gravity.

C.A. Wilkes and William Millar's improved "metallic compound for
flooring, paving, and other purposes," has for its object to provide a
paving compound which is not slippery or liable to soften in hot weather,
which sets rapidly, and is durable. To three parts of blast furnace slag
are added one part of hydraulic cement and enough water to give the
proper consistency. To each gallon of water used is added one part of
bittern water--the dregs from the manufacture of sea salt--or one part
of brine, or about 5 per cent. of carbonate of soda, and 21/2 per cent. of
carbonate of ammonia. In the compound they sometimes use potash in the
proportion of about 5 per cent. of the carbonate of ammonia and carbonate
of soda, and when potash is used with bittern water or brine, the
proportion of the latter is correspondingly reduced. The compound is of a
blue gray color; but when a more striking color is desired, red or yellow
oxide of iron may be added. When more speedy induration is necessary,
they add about 1 oz. of copperas to every gallon of compound used. The
claim is the admixture of bittern water, carbonate of soda, and carbonate
of ammonia with the washed slag and cement.

Another improvement, by C.A. Wilkes, relates, in laying _in situ_ any
metallic or other materials for street roadways, to completing the
convenience thereof by roughening or grooving the surfaces. The concrete
is laid in a plastic condition upon a bed of hard core, broken stone, or
preferably rough concrete. For footpaths the material may be laid in
convenient sections, say 4 ft. to 8 ft. square and 2 in. to 4 in. thick;
and in order to allow for the expansion of the material during the
setting of the sections or subsequent variations in temperature, he packs
the joints