In the fourth century, when bishop Theophilus broke to pieces the statues at Alexandria, he found some which were hollow, and placed in such a manner against a wall that a priest could slip unperceived behind them, and speak to the ignorant populace through their mouths'. I am acquainted with a passage which seems to imply that Cassiodorus, who, it is well known, constructed various pieces of mechanism, made also speaking machines; but I must confess that I do not think I understand the words perfectly2. That people ventured more than a hundred years ago to exhibit speaking machines for money, has been proved by Reitz in his annotations to Lucian, where he produces the instance of one Thomas Irson, an Englishman, whom he himself knew, and whose art excited much wonder in king Charles II. and his whole court. When the astonishment, however, became general, one of the pages discovered, in the adjoining chamber, a popish priest who answered in the same language, through a pipe, the questions proposed to the wooden head by whispering into its ear. This deception Irson often related himself3. I shall now add only a few observations respecting the Chinese shadows, which I have occasionally mentioned before. This ingenious amusement consists in moving, by pegs fastened to them, small figures cut out of pasteboard, the joints of which are all pliable, behind a piece of fine painted gauze placed before an opening in a curtain, in such a man 1 Theodoreti Hist. Eccles. v. 22. 2 Cassiodori Variar. i. ep. 45. 3 [Speaking Automaton.-There is a piece of mechanism now exhibiting to the public at the Egyptian Hall-the work of Professor Faber, of Vienna, and the result, as he states, of twenty-five years of labour and preparation. The name which he has given to this product of his ingenuity is the Euphonia; and the work, as that name implies, is another of those many combinations which have attempted, by the anatomical and physiological study of the structures that contribute to the human voice, to attain to an imitation of that organ as regards both sound and articulation. As an example of inductive and mechanical skill this exhibition is well deserving of attention. The professor himself, by an arrangement of bellows-pipes, pedal and keys, which he plays somewhat like the keys of a piano, prompts the discourse of his automaton; which certainly does enunciate both sounds and words. When we entered the room we found it singing to a select society. It requires all our sense of the ingenuity and perseverance which have been bestowed on the work to induce our assent to the proposition which calls the voice human; but undoubtedly it is a remarkable result of contriving skill and scientific patience.-Atheneum.] ner as to exhibit various scenes, according to pleasure; while the opening covered with gauze is illuminated, towards the apartment where the spectators sit, by means of light reflected back from a mirror; so that the shadows of the pegs are concealed. When it is requisite to cause a figure to perform a variety of movements, it is necessary to have several persons, who must be exceedingly expert. When a snake is to be represented gliding, the figure, which consists of delicate rings, must be directed at least by three assistants. This amusement, which one can hardly see the first time without pleasure, is really a Chinese invention. Many years ago, I have seen Chinese boxes on which such moveable figures were apparent only when the box was held against the light. In China, these shadows are used at the well-known feast of lanterns; and a description of them may be found in the works of some travellers. That they were common also in Egypt, we are informed by Prosper Alpinus', who admired them much; but he was not able to discover the method by which they were produced, as it was kept a secret. I was told by an Italian, who exhibited them at Göttingen some years ago, that they were first imitated, from the Chinese, at Bologna. ARTIFICIAL ICE. COOLING LIQUORS. THE art of preserving snow for cooling liquors during the summer, in warm countries, was known in the earliest ages. This practice is mentioned by Solomon, and proofs of it are so numerous in the works of the Greeks and the Romans, that it is unnecessary for me to quote them, especially as they have been collected by others3. How the repositories for keeping it were constructed, we are not expressly told; but what I know on the subject I shall here lay before the reader. That the snow was preserved in pits or trenches, is asserted 1 Historia Ægypti Natural. Lugd. Bat. 1735, 4to, p. 60. 2 Proverbs, xxv. ver. 13. 3 Bartholini de Nivis Usu Medico Observationes, Hafn. 1661. by many1. When Alexander the Great besieged the city of Petra, he caused thirty trenches to be dug and filled with snow, which was covered with oak branches, and which kept in that manner for a long time 2. Plutarch says that a covering of chaff and coarse cloth is sufficient3; and at present a like method is pursued in Portugal. Where the snow has been collected in a deep gulf, some grass or green sods, covered with dung from the sheep-pens, is thrown over it; and under these it is so well preserved, that the whole summer through it is sent the distance of sixty Spanish miles to Lisbon1. When the ancients therefore wished to have cooling liquors, they either drank the melted snow or put some of it in their wine, or they placed jars filled with wine in the snow, and suffered it to cool there as long as they thought proper. It appears that in these trenches it could not remain long clean; on the contrary, it was generally so full of chaff, that the snow-water was somewhat coloured with it, and had a taste of it, and for this reason it was necessary to strain either it or the wine that had been cooled by it5. That ice also was preserved for the like purpose, is probable from the testimony of various authors; but it appears not to have been used so much in warm countries as in the northern. Even at present snow is employed in Italy, Spain, and Portugal; but in Persia, ice7. I have never anywhere found an account of Grecian or Roman ice-houses. By the writers on agriculture they are not mentioned. Mankind however soon conceived the idea of cooling water without snow or ice, from having remarked that it became cold more speedily when it had been previously boiled, or at least warmed, and then put in a vessel among snow, or in a place much exposed to the air. Pliny seems to give this as an invention of Nero; and a jocular expression in Sueto1 Seneca, Quæst. Natur. iv. 13. 2 Athenæus, iii. p. 124. 3 Sympos. vi. quæst. 6.-Augustinus De Civitate Dei, xxi. 4, p. 610. * Mémoires Instructifs pour un Voyageur. How the snow repositories at Constantinople are constructed, is related by Bellon in his Observat. iii. 22. 5 The dissipated Heliogabalus caused whole mounts of snow to be heaped up in summer in order to cool the air. See Lampridius, Vita Heliogab. 6 Plin. xix. 4.—Latinus Pacatus in Panegyr. Theodos. cap. 23. 7 De la Valle, iii. p. 60, where the Persian ice-pits are described, as well as in Chardin, iv. p. 195. 8 Hist. Nat. xxxi. 3, 23, p. 552. nius' makes it at any rate probable that he was fond of water cooled by this method; but it appears to be much older. It seems to have been known even to Hippocrates: at least Galen 2 believes so. And Aristotle was undoubtedly acquainted with it; for he says that some were accustomed, when they wished water to become soon cold, to place it first in the sun and suffer it to grow warm. He relates also that the fishermen near the Black Sea poured boiling water over the reeds which they used in fishing on the ice to cause them to freeze sooner. Galen on this subject is still more precise. He informs us that the above practice was not so much used in Italy and Greece, where snow could be procured, as in Egypt and other warm countries, where neither snow nor cool springs were to be found. The water after it had been boiled was put into earthen vessels or jars, and exposed in the evening on the upper part of the house to the night air. In the morning these vessels were put into the earth (perhaps in a pit), moistened on the outside with water, and then bound round with fresh or green plants, by which means the water could be preserved cool throughout the whole day. Athenæus, who gives a like account from a book of Protagorides, remarks, that the pitchers filled with water, which had become warm by standing all day long in the sun, were kept continually wet during the night, by servants destined to that office, and in the morning were bound round with straw. In the island of Cimolus, water which had become warm in the day-time was put into earthen jars, and deposited in a cool cellar, where it grew as cold as snow. It was generally believed therefore, that water which had been warmed or boiled, was soonest cooled, as well as acquired a greater degree of refrigeration; and on this account boiled water is mentioned so often in the works of the ancients7. The same opinion prevails at present in the southern countries of Asia, and people there still let their water boil before they expose it to the air to cools. The experiments however 1 Vita Neronis, cap. 48: Hæc est Neronis decocta. 2 In lib. vi. Hippocrat. de Morbis Vulgar. comment. 4, 10. 3 Meteorol. i. cap. 12. 5 Deipnos. iii. p. 124. 4 In the place before quoted. 7 See Pitisci Lex. Antiq. Rom. under the word Decocta. which have been made on this subject by philosophers, have proved very different in the result. When one indeed places boiling and cold water, all other circumstances being equal, in frosty air, the latter will become ice before the former has cooled; but when one exposes to the cold, water that has been boiled, and unboiled water of equal temperatures, the former will be converted into ice somewhat sooner. The experiments made by Mariotte', Perrault, the Academy del Cimento3, Marian and others, showed no perceptible difference in the time of freezing, between boiled and unboiled water; but the former produced ice harder and clearer, the latter ice more full of blisters. In later times, Dr. Black of Edinburgh has, from his experiments, asserted the contrary. Boiled water, he says, becomes ice sooner than unboiled, if the latter be left at perfect rest; but if the latter be stirred sometimes with a chocolate stick, it is converted into ice as soon as the former. This difference he explains in the following manner:-Some motion promotes congelation; this arises in the boiled water through its re-imbibing air; and therefore it must necessarily freeze before the unboiled, provided the latter be kept at perfect rest. Fahrenheit had before remarked that water not moved, would show a cold several degrees below the freezing-point, without becoming ice. M. Lichtenberg, with whom I conversed on these contradictory results, assured me that he was not surprised at this difference in the experiments. The time of congelation is regulated by circumstances, with which philosophers are not yet sufficiently acquainted. A certain, but not every degree of stirring hastens it; so that every icy particle which is formed on the side of the vessel, or which falls from the atmosphere, may convert the water sufficiently cooled into ice instantaneously; and such unavoidable accidents must, where all other circumstances are equal, cause a great difference in the period of freezing. I am inclined to think that the cooling of water, in ancient 1 Traité du Mouvement des Eaux. 2 Du Hamel, Hist. de l'Academ. 1. i. c. 3, p. 99. 3 Tentamina Experimentorum Acad. del Cim. p. 183. 4 Dissertation sur la Glace. Paris, 1749, 12mo, p. 187. VOL. II. L |