There were several explosive mixtures. Automatic fire was made from equal parts of sulphur, saltpetre, and sulphide of antimony, finely pulverized and mixed into a paste, with equal parts of juice of the black sycamore and liquid asphaltum, a little quick-lime being added. It was directed to keep the material from the rays of the sun, which would set it on fire.
Of liquid or Greek fire we have not a precise description, since the knowledge of it was kept at Constantinople as a state secret. There is reason, however, to believe that it contained sulphur and nitrate of potash mixed with naphtha. Of gunpowder, Marcus Græcus, whose date is probably to be referred to the close of the eighth century, gives the composition explicitly. He directs us to pulverize in a marble mortar one pound of sulphur, two of charcoal, and six of saltpetre. If some of this powder be tightly rammed in a long narrow tube closed at one end, and then set on fire, the tube will fly through the air: this is clearly the rocket. He says that thunder may be imitated by folding some of the powder in a cover and tying it up tightly: Incombustible men. this is the cracker. It thus appears that fireworks preceded fire-arms. To the same author we are indebted for prescriptions for making the skin incombustible, so that we may handle fire without being burnt. These, doubtless, were received as explanations of the legends of the times, which related how miracle-workers had washed their hands in melted copper, and sat at their ease in flaming straw.
Arabian chemists.
Among the Saracen names that might be mentioned as cultivators of alchemy, we may recall El-Rasi, Ebid Durr, Djafar or Geber, Toghragé, who wrote an alchemical poem, and Dschildegi, one of whose works bears the significant title of "The Lantern." The definition of alchemy by some of these authors is very striking: the science of the balance, the science of weight, the science of combustion.
Djafar discovers nitric acid and aqua regia,
To one of these chemists, Djafar, our attention may for a moment be drawn. He lived toward the end of the eighth century, and is honoured by Rhazes, Avicenna, and Kalid, the great Arabic physicians, as their master. His name is memorable in chemistry, since it marks an epoch in that science of equal importance to that of Priestley and Lavoisier. He is the first to describe nitric acid and aqua regia. Before him no stronger acid was known than concentrated vinegar. We cannot conceive of chemistry as not possessing acids. Roger Bacon speaks of him as the magister magistrorum. He has perfectly just notions of the nature of spirits or gases, as we call them; thus he says, "O son of the doctrine, and that oxidation increases weight. when spirits fix themselves in bodies, they lose their form; in their nature they are no longer what they were. When you compel them to be disengaged again, this is what happens: either the spirit alone escapes with the air, and the body remains fixed in the alembic, or the spirit and body escape together at the same time." His doctrine respecting the nature of the metals, though erroneous, was not without a scientific value. A metal he considers to be a compound of sulphur, mercury, and arsenic, and hence he infers that transmutation is possible by varying the proportion of those ingredients. He knows that a metal, when calcined, increases in weight, a discovery 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 He solves the problem of potable gold. 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.
Rhazes discovers sulphuric acid.
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.
Geological views of Avicenna.
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 they are the effect of water, which, cutting for itself a new route, has denuded the valleys, the strata being of different kinds, some soft, some hard. The winds and waters disintegrate the one, but leave the other intact. Most of the eminences of the earth have had this latter origin. It would require a long period of time for all such changes to be accomplished, during which the mountains themselves might be somewhat diminished in size. But that water has been the main cause of these effects is proved by the existence of fossil remains of aquatic and other animals on many mountains." Avicenna also explains the nature of petrifying or incrusting waters, and mentions ærolites, out of one of which a sword-blade was made, but he adds that the metal was too brittle to be of any use. A mere catalogue His works indicate the attainment of the times. of some of the works of Avicenna will indicate the condition of Arabian attainment. 1. On the Utility and Advantage of Science; 2. Of Health and Remedies; 3. Canons of Physic; 4. On Astronomical Observations; 5. Mathematical Theorems; 6. On the Arabic Language and its Properties; 7. On the Origin of the Soul and Resurrection of the Body; 8. Demonstration of Collateral Lines on the Sphere; 9. An Abridgment of Euclid; 10. On Finity and Infinity; 11. On Physics and Metaphysics; 12. An Encyclopædia of Human Knowledge, in 20 vols., etc., etc. The perusal of such a catalogue is sufficient to excite profound attention when we remember the contemporaneous state of Europe.