OF PYRITES AND GYPSUM. 307
offer will therefore deal mainly with the natural history of
Pyrites and Gypsum. These two minerals are well developed
in the London Clay, and the London Clay is well developed in
Essex.
PYRITES.
Concerning Pyrites a vast deal has been written. Nearly
180 years ago there was published in Saxony a remarkable
treatise on this mineral, the work of a learned mineralogist, Dr.
Johann Friedrich Henckel, of Freiberg. Henckel (or Henkel)
was born at Merseburg in 1679, and after studying medicine at
Leipzig settled down in the little mining town of Freiberg,
where, yielding to the influence of his environment, he threw
himself with enthusiasm into the study of minerals, metals, and
mines. He was a voluminous writer. In 1725 he published the
famous work to which I have referred under the title of
Pyritologia. The author died in 1744, but a new and improved
edition of the great treatise was published posthumously, and so
wide became the reputation of the book that in 1757 Pyritologia
was translated into English, and three years later into French.
In the preface to the English issue, the translator explains
that the work should be welcomed by "those who are lovers of a
solid knowledge of nature, the genuine result of observation and
experiment." Now it strikes me that a "solid knowledge of
nature" is exactly the kind of thing that will commend itself to
the members of the Essex Field Club. No apology therefore
seems necessary for introducing Henckel's work, especially as it
is not likely to be familiar to any but those few folk who happen
to be interested in the history of mineralogy.
Although Henckel's translator, holding of course a brief for
his author, extols the Pyritologia as "a pattern worthy of copying
after in our enquiries into Nature, and a just specimen of the
method of induction," he is yet obliged to admit that the work is so
prolix as to need a free exercise of editorial surgery in the matter
of excision. In fact the editor drops the remark that Henckel is
"certainly but an indifferent writer ; diffuse to a fault, and
generally very obscure and perplex in his manner of writing,"
with a "strain of low pleasantry and affectation of learning."
This is certainly a formidable indictment and rather tends to repel
the reader from attacking the great monograph ; but though one
dreads having to encounter an author who is "obscure and