and of special importance was copper, the _Venus_ of the early chemists.

The medicinal virtue which inhered in Butler's stone and in other
powerful fermental remedies, van Helmont designated as "drif," which he
said means, in the vernacular, virgin sand or earth. This virtue
requires a metallic body in which to inhere. The general concept is not
unfamiliar, of a virtue or power or ferment which was attached to a
material object, and it is this type of explanation which was so
preponderant in, for example, Porta's _Natural Magick_. Van Helmont
speaks of the "first being," which translates the Latin _Ens_, of Venus
or copper. Vitriol is the basic substance, and for purification of the
virtue we require a "sequestration of its Venus from the dregs of the
vitriol."[62]

This was the background from which Boyle set about to secure a potent
remedy. Van Helmont had discussed his experiments whereby he tried to
create a medicine which would have the virtues of Butler's stone. Boyle
attempted to improve on van Helmont's technique. Copper--Venus--was the
basic metal, and Boyle started with vitriol or copper sulfate. He gave
fairly explicit directions for the preparation, including calcination,
boiling, drying, adding sal armoniack, subliming twice. The resulting
chemical represented a purified medicine which he prescribed in variable
dosage, from two or three grains, up to twenty or thirty at the maximum.
He declared it to be a "potent specifick for the rickets," since he, and
others to whom he had given it for use, had "cured" a hundred or more
children of that disease. The medicine he also prescribed in fevers and
headache, and he thought it "hath done wonders" in obstinate
suppressions of the menses. It also improved the appetite. It worked, he
declared, through the sweat and, to some extent, the urine.[63] It is
noteworthy that Boyle did not claim to have cured the same illnesses
than van Helmont reports as having been cured by Butler's stone.

As another example, he gave directions for preparing essence of
hartshorn--prepared, literally, from the horn itself. The preparation,
strongly alkaline, he prescribed in small doses of eight to ten drops.
The medicine "resists malignity, putrefaction, and acid humours," for
it destroys the acidity. He used it "in fevers, coughs, pleurisies,
obstructions of the spleen, liver, or womb, and principally in
affections of the brain...."[64]

While Boyle was a far more skillful chemist