pieces of stone, so arranged as to form blind drains for the removal
of any water which might find its way under the floor.

Toward the top of this filling, finer stones were used, then about
three inches of gravel, which was covered with two inches of sand and
lime. Two years ago I was at this mill when some alterations requiring
the removal of the floor were in progress, and found that the lumber
was still in good, sound condition, except for a superficial decay on
the under side of the floor plank.

But there are frequent instances where it is necessary to place the
floor directly upon the earth, without any space or loose filling
underneath it, in order to save room, or to secure a firm support for
machinery. By way of information upon what has actually been
accomplished in this direction, I will cite instances of three floors
in such positions, all of which have to my knowledge fulfilled the
purpose for which they were designed.

The first instance is that of a basement floor laid twenty-one years
ago, a portion of which was made by excavating one foot below the
floor, six inches of coarse stone being filled in, then five inches of
coal tar concrete made up with coarse gravel, and finally about one
inch of fine gravel concrete. Before the concrete was laid, heavy
stakes were driven through the floor about three feet apart, to which
the floor timbers were nailed and leveled up. The concrete was then
filled in upon the floor timbers, and thoroughly tamped and rolled out
to the level of the top of the floor timbers. The under side of the
floor timbers was covered with hot coal tar.

This floor is still in good condition, and has not needed repairs
caused by the decay of the timber. Another portion of the floor laid
at the same time and in the same manner, with the exception that
cement concrete was used in the place of the coal tar, was entirely
rotted out in ten years.

Another floor was made in quite a similar manner. All soil and loam
was removed from the interior of the building; the whole surface was
brought up to the grade with a puddle of gravel and ashes; stakes two
and a half by four inches, and thirty inches in length, were driven
down; and nailing strips were secured to them. Over this puddled
surface a coat of concrete eight inches thick was laid, the top being
flush with the upper surface of the nailing strips. This concrete was
made of pebbles about two inches in diameter, well coated with coal
t