PRACTICAL PAPERS—ARTIFICIAL STONE. 
369 
mixed with silicate of soda, turn both into flint, or something very much like 
it, the road was clear, and the manufacture of stone from sand was as simple 
and as beautiful a process as the making of Bessemer steel from pig-iron by 
blowing air through it when in the melted state. 
“ During the month of June, 1867, on the occasion of a visit of a party of 
about one hundred and eighty gentlemen, comprising heads of public offices 
and boards, chemists, geologists, engineers, architects, and others, to the new 
works of the Patent Concrete Stone Company at East Greenwich, Mr. Ran- 
some showed and explained the whole process of making stone from sand, 
and exhibited some hundreds of the objects and ornameuts, many of them of 
great beauty, already made to the order of architects and builders for various 
new buildings in England and abroad. 
“The sand, a clean-grained, slightly brownish sort, just such as a dishonest 
grocer might select for increasing the gravity, specific or otherwise, of his 
ugar, comes from near Maidstone. There is no end to the quantity of it, 
and we believe it costs less than three shillings a ton in the Thames. There 
are flints enough for a hundred years to come brought up froni the chalk pits 
at Charlton ; and the caustic soda and the chloride of calcium, the latter a 
waste product of the soda manufacture, are bought of the wholesale chemists. 
The silicate of soda is made from the flints and caustic soda as follows: The 
flints are heaped upon iron gratings within a series of cylindrical digesters, 
of the material, size, and form of smalt steam-boilers. A solution of caustic 
soda is then added; the digester’s then closed steam-tight, and the contents 
are boiled by steam of seventy pounds taken from a neighboring boiler and 
led through the solution in a coil of iron pipes. The solution of causticsoda 
is prepared of a specific gravity of about 1.200. The flints are dissolved into 
‘solubleglass,’ and are drawn off in that state as a clear though imperfectly 
liquid substance, which is afterwards evaporated to a treacly consistency and 
color, and of a specific gravity of 1.700. 
“The sand is completely dried, at the rate of two tons an hour, within a 
revolving cylinder, through which hot air is forced by a centrifugal fan. A 
small portion of finely ground carbonate of lime, say Kentish rag, or even 
chalk, is mixed with the sand, the more closely to fill the interstices; and 
each bushel of the mixture is worked up in a loam mill along with a gallon 
of the silicate of soda. Thoroughly mixed with this substance, the sand has 
a sticky coherence, sufficien<^^ .to enable it to be moulded to any form, and, 
when well rammed, to retain its shape, if very carefully handled. In this 
condition—moulded, of course, and anything that can be done in founder’s 
loam may be done in this sand, sticky with silicate of soda—in this condition 
it is ready for the solution of chloride of calcium. The instant this is 
poured upon the moulded sand, induration commences. In a minute or so 
little lumps of sand, so slightly stuck together by the silicate of soda that 
they could hardly be kept from falling to pieces within the fingers, wore solidi¬ 
fied into pebbles so hard that they might be thrown against a wall without breakj 
ing, and only a short further saturation was necessary to indurate them 
Ag. Tr.—24. 
