cost, especially in
the better classes of work; all of which is effected with less plant
than ordinarily required. For engineering work, such as sea walls, the
hexagonal slabs, made of greater thickness than those employed for
ordinary walling, will answer admirably, especially if the grooves be
made proportionately larger. By the use of these slabs the work may be
built up with great rapidity. For small domestic work, such as the
dwellings of artisans, these slabs; which are of such a form as to
render them easy of transport, may be supplied to the workmen themselves
in order that they may erect their own dwellings, as, on account of the
simplicity of this system and the absence of need of plant, any
intelligent mechanic can do the work.

Any arrangement of independent scaffolding may be employed for this
system, but that invented specially for the purpose by Mr. Frank West,
as shown in Fig. 26 of our engravings, is to be preferred. It not only
supplies the necessary scaffold, but also the necessary arrangements for
hoisting the slabs, as well as for raising the liquid concrete and
depositing it behind the slabs. It is really an independent scaffold,
and may be used wherever a light tramway of contractor's rails can be
laid, which in crowded thoroughfares would of necessity be upon a
staging erected over the footway. The under frame is carried upon two
bogie frames running upon the contractor's rail, by which means it is
enabled to turn sharp curves, a guide plate inside the inner rail being
provided at the curves for this purpose. The scaffold itself consists of
a climbing platform made to travel up or down by means of four posts
which have racks attached to their faces, and which are fixed to the
under frame and securely braced to resist racking strains. A worm
gearing, actuated by a wheel on the upper side of the scaffold, causes
the scaffold to ascend or descend. A railgrip, made to act at the curves
as well as on the straight portions of the rail by being attached to a
radial arm fixed to the under frame, assists the stability of the
scaffold where required, but the gauge of the rails is altered to render
the scaffold more or less stable according to its height. Combined with
the same machine, and traveling up and down one of the same posts used
for the scaffold, is an improved crane. Its action depends upon the
proposition in geometry that if the length of the base of a triangle be
altered, its angles, and there