Painting on Glass.—This art, so far as it depends upon chemistry, was carried formerly to high perfection. Of this we have striking instances in the windows of ancient churches, where paintings present themselves in the most vivid colours, without detracting from the transparency of the glass. Boerhave and others observe, that we have lost the secret to such a degree, that there are scarcely any hopes of recovering it. Late experiments go far towards a successful restoration of this art.
Democritus.—This eminent man, who was a native of Abdera in Thrace, flourished upwards of four centuries before the Christian æra. For the sake of acquiring wisdom he travelled into Egypt, and abode with the priests of the country. He may be deemed the father of experimental philosophy. It is affirmed that he extracted the juice of every simple, and that there was not a quality belonging to the mineral or vegetable kingdoms that escaped his notice. Seneca says, that he was the inventor of reverberating furnaces, the first who gave a softness to ivory, and imitated nature in her production of precious stones, particularly the emerald.
Gunpowder.—Virgil and his commentator Servius, Hyginus, Eustathius, La Cerda, Valerius Flaccus, and many other authors, speak in such a manner of Salmoneus’s attempts to imitate thunder, as suggest to us that he used a composition of the nature of gunpowder. He was so expert in mechanics, that he formed machines which imitated the noise of thunder, and the writers of fable, whose surprise in this respect may be compared to that of the Mexicans when they first beheld the fire-arms of the Spaniards, give out that Jupiter, incensed at the audacity of this prince, slew him with lightning. It is much more natural to suppose that this unfortunate prince, as the inventor of gunpowder, gave rise to these fables, by having accidentally fallen a victim to his own experiments. Dion and Joannes Antiochenus report of the emperor Caligula, that he imitated thunder and lightning by means of machines, which at the same time emitted stones. Themistius relates, that the Brachmans encountered one another with thunder and lightning, which they had the art of launching from on high at a considerable distance. Agathias reports of Anthemius Traliensis, that having fallen out with his neighbour, Zeno the rhetorician, he set fire to his house with thunder and lightning. Philostrates, speaking of the Indian sages, says, that when they were attacked by their enemies they did not leave their walls to fight them, but repelled and put them to flight by thunder and lightning. In another place he alleges that Hercules and Bacchus attempting to assail them in a fort where they were entrenched, were so roughly received by reiterated strokes of thunder and lightning, launched upon them from on high by the besieged, that they were obliged to retire. The effects ascribed to these engines could scarcely be brought about but by gunpowder. In Julius Africanus there is a receipt for an ingenious composition to be thrown upon an enemy, very nearly resembling that of gunpowder. But that the ancients were acquainted with it seems proved beyond doubt, by a clear and positive passage of an author called Marcus Græcus, whose work in manuscript is in the Royal Library at Paris, entitled “Liber Ignium.” The author, describing several ways of encountering an enemy, by launching fire upon him, among others gives the following receipt:—Mix together one pound of live sulphur, two of charcoal of willow, and six of saltpetre; reduce them to a very fine powder in a marble mortar. He directs a certain quantity of this to be put into a long, narrow, and well-compacted cover, and so discharged into the air. Here we have the description of a rocket. The cover with which thunder is imitated he represents as short, thick, but half-filled, and strongly bound with packthread, which is exactly the form of a cracker. He then treats of different methods of preparing the match, and how one squib may set fire to another in the air, by having it enclosed within it. In short, he speaks as clearly of the composition and effects of gunpowder as any body in our times could do. This author is spoken of by Mesue, an Arabian physician, who flourished in the beginning of the ninth century. There is reason to believe that he is the same of whom Galen speaks.
Generation.
There are two theories on this subject among the moderns. Harvey, Stenon, Graaf, Redi, and other celebrated physicians, maintain that all animals are oviparous, and spring from eggs, which in the animal kingdom are what seed is in the vegetable. Hartsoëker and Lewenhoek are of a different opinion, and maintain that all animals spring by metamorphosis from little animals of extreme minuteness.
The first of these systems is merely a revival of that taught by Empedocles, as cited by Plutarch and Galen, and next to him Hippocrates, Aristotle, and Macrobius. The other system, that of animalcula or spermatic vermiculi, is but a revival of the opinions of Democritus and other ancients.
Hippocrates, founding himself upon a principle universally received by antiquity that nothing arises from nothing, advanced that nothing in nature absolutely perished; that nothing, taking it altogether, was produced anew; nothing born, but what had a prior existence; that what we call birth, is only such an enlargement as brings from darkness to light, or renders visible, those small animalcula which were before imperceptible. He maintains that every thing increases as much as it can, from the lowest to the highest degree of magnitude. These principles he afterwards applies to generation, and declares that the larger sizes arise out of the lesser; that all the parts successively expand themselves, and grow and increase proportionally in the same series of time; that none of them in reality takes the start of another, so as to be quicker or slower in growth; but that those which are naturally larger sooner appear to the eye, than those which are smaller, though they by no means preceded them in birth or existence.
Polypi.—The multiplicity of animation of which the polypus is capable, supposed to have been discovered by the moderns, was known to the ancients. There are passages of Aristotle and St. Augustine, wherein they speak of it as a thing which they knew from their own experience. The latter, in his book entitled “De Quantitate Animæ,” relates, that one of his friends performed the experiment before him of cutting a polypus in two; and that immediately the separated parts betook themselves to flight, moving with precipitation, the one one way, and the other another. Aristotle, speaking of insects with many feet, says, that there are of these animals or insects, as well as of plants and trees, that propagate themselves by shoots: and as what were but the parts of a tree before, become thus distinct and separate trees; so in cutting one of these animals, says Aristotle, the pieces which before composed altogether but one animal, become all of a sudden so many different individuals. He adds, that the animating principle in these insects is in effect but one, though multiplied in its powers, as it is in plants.
The Sexual System of Plants.
Vivunt in Venerem frondes, omnesque vicissim
Felix arbor amat, nutant ad mutua palmæ
Fœdera, populeo suspirat populus ictu,
Et platani platanis, alnoque assibilat alnus.