calcined in powder, thereby avoiding the production of such a hard
clinker, which has afterward to be broken up and reduced to a fine
powder by grinding in an ordinary mill?

The foregoing are some of the defects which the author applied himself
to remove, and he now desires to draw attention to the way in which
the object has been attained by the substitution of a revolving
furnace for the massive cement kilns now in general use, and by the
application of gaseous products to effect calcination, in the place of
coke or other solid fuel. The revolving furnace consists of a
cylindrical casing of steel or boiler plate supported upon steel
rollers (and rotated by means of a worm and wheel, driven by a pulley
upon the shaft carrying the worm), lined with good refractory fire
brick, so arranged that certain courses are set so as to form three or
more radial projecting fins or ledges. The cylindrical casing is
provided with two circular rails or pathways, turned perfectly true,
to revolve upon the steel rollers, mounted on suitable brickwork, with
regenerative flues, by passing through which the gas and air severally
become heated, before they meet in the combustion chamber, at the
mouth of the revolving furnace. The gas may be supplied from slack
coal or other hydrocarbon burnt in any suitable gas producer (such,
for instance, as those for which patents have been obtained by Messrs.
Brook & Wilson, of Middlesbrough, or by Mr. Thwaite, of Liverpool),
which producer may be placed in any convenient situation.

The cement mixture or slurry, instead of being burnt in lumps, is
passed between rollers or any suitable mill, when, it readily falls
into coarse dry powder, which powder is thence conveyed by an elevator
and fed into the revolving furnace by means of a hopper and pipe,
which, being set at an angle with the horizon, as it turns gradually