The standard adopted for compressive test pieces in the 10,000,000-lb.
machine is a prism, having a base of 12 in. and being 24 in. high. The
tests include not only those for compression or crushing strength, but
also those for resistance to compressive strains of the prisms and
cubes, when raised to high temperatures in muffles or kilns; resistance
to weathering, freezing, and thawing; porosity; fire-resisting
qualities, etc.
In collecting field samples, special attention is paid to the occurrence
of the stone, extent of the deposit, strike, dip, etc., and specimens
are procured having their faces cut with reference to the bedding
planes, in order that compressive and weathering tests may be made, not
only in relation to these planes but at those angles thereto in which
the material is most frequently used commercially. Attention is also
paid to the results of blasting, in its relation to compressive strains,
as blasting is believed to have a material effect on stones, especially
on those which may occur in the foundations of great masonry dams, and
type specimens of stone quarried by channeling, as well as by blasting,
are collected and tested.
_Clay and Clay Products Investigations._--These investigations are in
charge of Mr. A. V. Bleininger, and include the study of the occurrence
of clay beds in various parts of the United States, and the adaptability
of each clay to the manufacture of the various clay products.
Experiments on grinding, drying, and burning the materials are conducted
at the Pittsburg testing station, to ascertain the most favorable
conditions for preparing and burning each clay, and to determine the
most suitable economic use to which it may be put, such as the
manufacture of building or paving bricks, architectural tiles, sewer
tiles, etc.
The laboratory is equipped with various grinding and drying devices,
muffles, kilns, and apparatus for chemical investigations, physical
tests, and the manufacture and subsequent investigative tests of clay
products.
This section occupies the east end of Building No. 10, and rooms on the
first and second floors have been allotted for this work. In addition, a
brick structure, 46 by 30 ft., provided with a 60-ft. iron stack, has
been erected for housing the necessary kilns and furnaces.
[Illustration: PLATE XVI.
Fig. 1.--Brick Machine and Universal Cutter.