be bedded or jointed in cement,
and, provided temporary ties be placed across their upper edges to
connect the slabs forming each face of the wall together, the space
between the faces of the wall may then be filled in with the plastic
concrete.

All these devices, however, are not of permanent utility; they are only
temporarily required (i.e., up to the time that the beton has become
hard and formed a permanent traverse tie between the two faces of the
wall), for it is manifest that the ultimate object of all slab concrete
construction is: (a) To retain and to mould the plastic concrete used in
forming the wall; (b) to key or fix the slabs to the mass which they
themselves have moulded; and (c) to form a facing to the wall. When
these objects shall have been accomplished, there is no further need of
any tie whatever beyond that which naturally obtains in a concrete wall.
In West's system, however, where the slabs are keyed course to course,
any kind of transverse tie to be used during the process of
construction, except that used in the starting course, is entirely
dispensed with, and the courses of slabs above depend solely upon the
courses of slabs below them for their stability and rigidity up to the
time that the plastic filling-in has been deposited and become hard
between both faces of the wall.

[Illustration: CONCRETE CONSTRUCTION]

There is, however, a more decided difference between West's system and
those previously in use, for it is marked by the fact that the slabs
composing the shell of the whole structure in many cases may be built up
before the filling-in is deposited between the slabs, and in none of the
other cases can this be done. In fact, only in the first two cases
before mentioned can more than one course of slabs be laid before
filling-in of some kind must be done. Compared with the ordinary method
of building in concrete, this system avoids: 1. The charge for use and
waste of wood casings; 2. finishing the face of the work (both inside
and outside) after the structure is raised, and, therefore, the
bursting-off of the finished face; and 3. the difficulties encountered
in working mouldings and other ornaments on the face of the work by the
ordinary plasterer's methods. It also provides a face of any of the
usual colors that may be obtained in concrete, besides a facing of any
other material, such as marble, etc., and produces better and more
durable work, at the same time showing a saving in