ry of the greatest importance,
as eventually brought to bear in the destruction of the doctrine of
Phlogiston of Stahl, and which has been imputed to Europeans of a much
later time. He describes the operations of distillation, sublimation,
filtration, various chemical apparatus, water-baths, sand-baths, cupels
of bone-earth, of the use of which he gives a singularly clear
description. A chemist reads with interest Djafar's antique method of
obtaining nitric acid by distilling in a retort Cyprus vitriol, alum,
and saltpetre. He sets forth its corrosive power, and shows how it may
be made to dissolve even gold itself, by adding a portion of sal
ammoniac. Djafar may thus be considered as having solved the grand
alchemical problem of obtaining gold in a potable state. Of course, many
trials must have been made on the influence of this solution on the
animal system, respecting which such extravagant anticipations had been
entertained. The disappointment that ensued was doubtless the reason
that the records of these trials have not descended to us.

[Sidenote: Rhazes discovers sulphuric acid.]

[Sidenote: Bechil discovers phosphorus.]

With Djafar may be mentioned Rhazes, born A.D. 860, physician-in-chief
to the great hospital at Bagdad. To him is due the first description of
the preparation and properties of sulphuric acid. He obtained it, as the
Nordhausen variety is still made, by the distillation of dried green
vitriol. To him are also due the first indications of the preparation of
absolute alcohol, by distilling spirit of wine from quick-lime. As a
curious discovery made by the Saracens may be mentioned the experiment
of Achild Bechil, who, by distilling together the extract of urine,
clay, lime, and powdered charcoal, obtained an artificial carbuncle,
which shone in the dark "like a good moon." This was phosphorus.

[Sidenote: Geological views of Avicenna.]

[Sidenote: His works indicate the attainment of the times.]

And now there arose among Arabian physicians a correctness of thought
and breadth of view altogether surprising. It might almost be supposed
that the following lines were written by one of our own contemporaries;
they are, however, extracted from a chapter of Avicenna on the origin of
mountains. This author was born in the tenth century. "Mountains may be
due to two different causes. Either they are effects of upheavals of the
crust of the earth, such as might occur during a violent earthquake, or
t