.
In the same way cold brine has been used with great success for
freezing quicksand in the sinking of shafts, the excavation being
carried out and the watertight tubing or lining put in while the
material is in a solid state. In a paper such as this it would be
quite impracticable to enter into details of construction, and the
author has therefore confined himself chiefly to principles of
working. In conclusion, however, it may be added that in ammonia
machines, whether on the absorption or compression systems, no copper
or alloy of copper can be used in parts subjected to the action of the
ammonia. Cast or wrought iron and steel may, however, be used,
provided the quality is good, but special care must be taken in the
construction of those parts of absorption machines which are subjected
to a high temperature. In both classes of apparatus first-class
materials and workmanship are most absolute essentials.

* * * * *

[Continued from Supplement, No. 646, p. 10319.]

ELEMENTS OF ARCHITECTURAL DESIGN.[1]

[Footnote 1: Delivered before the Society of Arts, London,
December 13, 1887. From the _Journal_ of the Society.]

BY H. H. STATHAM.

III.--CONTINUED.

The Romans, in their arched constructions, habitually strengthened the
point against which the vault thrust by adding columnar features to
the walls, as shown in Fig. 108; thus again making a false use of the
column in a way in which it was never contemplated by those who
originally developed its form. In Romanesque architecture the column
was no longer used for this purpose; its place was taken by a flat
pilaster-like projection of the wall (plan and section, Fig. 109),
which gave sufficient strength for the not very ambitious vaulted
roofs of this period, where often in fact only the aisles were
vaulted, and the center compartment covered with a wooden roof. At
first this pilaster-like form bore a reminiscence of a classic capital
as its termination; a moulded capping under the eaves of the building.
Next this capping was almost insensibly dropped, and the buttress
became a mere flat strip of wall. As the vaulting became bolder and
more ambitious, the buttress had to be made more massive and of
greater projection, to afford sufficient abutment to the vault, more
especially toward the lower part, where the thrust of the roof is
carried to the ground. Hence arose the tendency to increase the
projection of the buttres