tment of Ardennes, at Remogne,
Fumay, etc.

Normandy, Brittany, Dauphiny and Marne likewise possess quarries,
although they are not so productive.

The exploitation is commonly done in open quarry. After the vegetable
mould (which in this case is called "cover") has been removed, we meet
with a solid slate which it is difficult to split into laminae, and it
is not until a depth of at least fifteen feet is reached that we find
a material that is fit to be exploited. All the best beds of slate, in
fact, improve in quality in proportion as they lie deeper under the
surface, near to which they have little value. Without entering into
details as to the exploitation of this product, let us say that the
blocks have to be divided in the quarry, since, in the open air, they
rapidly lose the property of readily splitting into thin, even laminae.

[Illustration: SLATE STORE-VATS FOR BREWERIES.]

Slate has but slight affinity for water, and, moreover, resists
atmospheric influences, humidity and heat pretty well.

This property renders it valuable for a large number of domestic
purposes.

There is no certain proof, it is true, that it was employed by the
ancients, but it is, nevertheless, extremely probable that it was used
in mass at an early period for stair heads, pillars for buildings and
as a material for fencing.

The exploitation of the material became especially active at the
period when the idea occurred to some one to use slate for the rooting
of houses. It was employed for this purpose along with tiles as far
back as the eleventh century in the majority of schistose districts.
It is well known, for example, that Fumay (Ardennes) at this period
had a brotherhood of slate quarrymen.

A method of getting out the material and cutting it regularly was
found toward the end of the twelfth century, and it was not till then
that it became of general application. Moreover, with the advent of
the Gothic period slate became indispensable for castle roofs, which
have a conical form.

The best slate for roofing purposes is hard, heavy and of a bluish
gray color. A good slate should readily split into even laminae; it
should not be absorbent of water either on its face or endwise, a
property evinced by its not increasing perceptibly in weight after
immersion in water; and it should be sound, compact and not apt to
disintegrate in the air.

For a long time past there have been used in schools slate tablets
upon which the p