ivided into the "Bunter" and "Keuper"; the
lower division, the Bunter, occupying most of the ground about
Liverpool; the upper, the Keuper, being more developed on the Cheshire
side. All these sandstones are not fit for building purposes, and
those that are so used differ considerably in their durability. It is
my object in this short Paper to show upon what the perfection or
imperfection of the various stones for building purposes depends--a
matter of great moment to an architect or engineer who is desirous
that his work should last.

Sandstones, or, in masons' language, "free-stones," from the freedom
with which most of them are worked when freshly taken from the quarry,
are plastic or sedimentary rocks. That is, they are composed of
separate particles which have once existed as sand, like that we see
on our own shores, or in the sand dunes of Hoylake or Crosby.
Sandstones are usually more or less laminated, and are stronger to
transverse stress at right angles to their natural bedding than in any
other direction, a fact recognized in every architect's specification,
which states "all stones must be laid on their natural bed," a
direction that unfortunately sometimes begins and ends in the
specification. The cause of the superior strength is not, however,
generally understood.

I have devoted some considerable time to an investigation of the
internal structure of sandstones, which I have communicated from time
to time to various scientific societies and publications, and will now
briefly explain it in a manner I judge will be most likely to interest
architects and engineers. The particles or grains of which the rock is
built up are of various forms and sizes, from a thoroughly rounded
grain, almost like small shot, to a broken and jagged structure, and
to others possessing crystalline faces. These grains, most of them
possessing a longer axis, have been rolled backwards and forwards by
the tides or by river-currents. The larger grains naturally lie on
their sides when freshly deposited, with their axes in the plane of
bedding; the smaller and more rounded particles naturally tend to
occupy the interstices between the others, and in this way rude
divisional planes or laminations are formed. Each layer forms a sort
of course like coursed-rubble in a wall, and by the necessities of
deposition a certain rude geometric arrangement results, by which the
particles of the future rock overlap each other, and thereby gain wha