n which it was imbedded and itself is that in
the latter case the process of silicious deposit has gone further, so
that all the interstices between the grains have been absolutely
filled up with the cement.

It is not possible to see this clearly with the naked eye, but by the
aid of a slice of the rock prepared for the microscope the granular
structure of the quartzite is made perfectly plain. So much for the
mechanical, chemical, and molecular structure of sandstone, all of
which affect the strength and quality of the stone; but to architects
there is another element of consequence, namely, the color. The rich
red of our Triassic sandstones is due to a pellicle of peroxide of
iron coating each of the grains. That this is merely surface coloring
is shown by the fact that hydro-chloric acid will discharge the color
and leave the grains translucent. Unfortunately the most brilliantly
colored stone is not the most durable, and it so happens that these
brilliant red sandstones are often composed of exceedingly rounded
grains. Also some of the very red sandstone has an interfilling of a
loose argillaceous irony matter detrimental to the stone as a building
stone. The most durable of the red sandstones are those having a paler
or grayer hue, like those of Woolton, Everton, and Runcorn. This
distinction of color was brought freshly to my mind a short time since
in looking at the church of Llandyrnog, in the Vale of Clwyd, a few
miles from Ruthin. Some of the dressings, quoins for instance, were of
a very brilliant-colored red sandstone, and others of a pale gray or
purple red. It struck me that these latter must be of Runcorn stone,
which I was afterwards informed was the case. The very red stone was
the natural stone of the Vale, originally used for dressings, which
were replaced, on the restorations being made, with Runcorn stone. The
original stone was aesthetically the best, but the introduced stone the
best structurally. The old stone of Chester Cathedral was a very red
Bunter sandstone, which decayed badly. It has been replaced in the
restorations by Runcorn stone, which belongs to the Keuper division,
which has caused the Geological Surveyors to say that the Keuper is a
better building stone than the Bunter. In this case it is; but, on the
other hand, the Bunter sandstones, or Pebble-beds, as they are called,
near Liverpool, are often better than the Runcorn Keuper. The Runcorn
building stone lies between two beds of