OF PYRITES AND GYPSUM. 313
but likewise where it is loamy or clayie ; and this year 1728, I did not only
gather them from there myself, but did likewise see divers Boys gathering them
even at the Place where the Cliff is highest and most loamy ; and as every Tide
washeth away some of the looser Earth which falleth down from the Cavities of
the Cliff, those Stones being most ponderous are there left ; and as soon as the
Tide permits they busily gather them."
It is interesting to learn from Dale that "The Pyritae of Essex,
Kent, etc., yield upon Trial, a small quantity of Gold and Silver,
and some of them a little Copper."
Referring to the nodules of pyrites in the cliffs of London
Clay near Walton-on-the-Naze, Mr. Whitaker, writing in 1877,
tells us that they were then still collected on the beach for the
manufacture of copperas to the extent of about 150 tons a
year.9
The term "copperas" naturally suggests that the substance
so called contains copper, and this no doubt was originally the
case. But the word gradually acquired an extended meaning,
and, instead of being limited to copper sulphate, came to be
applied also to the corresponding salts of other metals. Hence
we recognise not only "blue copperas," or copper sulphate, but
"green copperas," or iron sulphate, and "white copperas," or
zinc sulphate—three salts known also respectively as blue
vitriol, green vitriol, and white vitriol. But the strangest thing
about the word "copperas" is that in the course of its history it
has come to be almost limited to the iron-salt, so that the other
compounds just mentioned are rarely called copperas at the
present day. If we use the word "copperas" without any
qualification we invariably mean sulphate of iron : in other words
our copperas contains no copper. In Dr. Murray's great
National Dictionary it is pointed out (sub voce) that the extension
of meaning took place anterior to the appearance of the word in
English, for iron sulphate was included under the Greek word
Calkanqon and the Latin chalcanthum. In the explanation
of the term, however, there is a slight error, for reference is made
to "the dissolving of iron by a solution of green copperas with
deposition of its copper"—a passage in which the word "green"
should obviously be "blue," for it must be the copper sulphate
and not the iron-salt that is meant.
With regard then to the old copperas-houses of Walton, let
9 The Geology of the Eastern End of Essex (Walton Naze and Harwich), Memoirs of the
Geological Survey. 1887, p. 8.