The population of the city is
about 400,000. It contains many magnificent buildings. Our engraving
is from _Illustrirte Zeitung_.

[Illustration: THE PUERTA DEL SOL, MADRID, SPAIN (From a Photograph.)]

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CONCRETE BUILDINGS FOR FARMS.

Buildings made of concrete have never received the attention in this
country that they deserve. They have the merit of being durable and
fire-proof, and of not being liable to be blown down by violent winds.
It is very easy to erect them in places where sand and gravel are near
at hand and lime is comparatively cheap. Experiments made in England
show that coal screenings may be employed to good advantage in the
place of sand and gravel. Mr. Samuel Preston, of Mount Carroll, Ill.,
has a dwelling and several other buildings made of concrete and
erected by himself. They were put up in 1851, and are in excellent
condition. In _The Farmers' Review_ he gives the following directions
for building concrete walls:

First, secure a good stone foundation, the bottom below frost, the top
about one foot above ground. Near the top of the foundation bed in 2x4
scantling edgewise transversely with the walls, at such distances
apart as the length of the planks that form the boxes to hold the
concrete may require, the ends of the scantling to run six inches
beyond the outside and inside of the wall. Now take 2x6 studding, one
foot longer than the height of the concrete walls are to be, bolt in
an upright position in pairs to each end of the 2x4 scantling, and, if
a foot wall is to be built, sixteen inches apart, as the box plank
will take up four inches. To hold the studding together at the top,
take pieces of 2x6 lumber, make two mortises in each piece large
enough to slip easily up and down on the studding, forming a tie. Make
one mortise long enough to insert a key, so that the studding can be
opened at the top when the box plank are to be raised. When the box
plank are in position, nail cleats with a hole in each of them on each
side of the studding, and corresponding holes in the studding, into
which insert a pin to hold the plank to the studding. Bore holes along
up in the studding, to hold the boxes when raised.

To make the walls hollow, and I would do it in a building for any
purpose, use inch boards the same width of the box plank, one side
planed; put the two rough sides together with shingles between,
nailing them together with six-penny na