small, they occupy little room, they can be placed at any reasonable
distance from the place where the gas is to be burnt; any laborer can
shovel the slack into them, and they do not require constant skilled
supervision. It is claimed by the author of this paper that the
following are among the many advantages derivable from the adoption of
this method of manufacturing Portland cement, as compared with the old
system:

(1) Economy of space--the furnaces, with their appurtenances,
requiring only about one-fourth the space of what would be
occupied by the ordinary kilns for producing the same quantity
of finished cement.

(2) Continuous working, and consequent economy of fuel lost by
cooling and subsequent reheating of the kiln walls.

(3) Economy of repairs, which are of a simple and comparatively
inexpensive character, and of much less frequent occurrence, as
the continuous heat avoids the racking occasioned by the
alternate heating and cooling.

(4) Economy in first cost.

(5) Economy in grinding, a friable granular substance being
produced instead of a hard clinker, whereby crushers are quite
abolished, and the wear and tear of millstones greatly
reduced.

(6) Economy of labor, the conveyance to and removal from, the
revolving furnace being conducted automatically by mechanical