A History of Inventions, Discoveries, and Origins, Volume II (of 2). Johann Beckmann

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СКАЧАТЬ We know at present that coolness is produced by evaporation. A thermometer kept wet in the open air falls as long as evaporation continues387. With sulphuric æther, and still better with that of nitre, which evaporates very rapidly, water may be made to freeze even in the middle of summer; and Cavallo saw in summer a Fahrenheit’s thermometer, which stood at 64°, fall in two minutes, by means of æther, to +3, that is to 29° below the freezing-point388.

      On this principle depends the art of making ice at Calcutta and other parts of India, between 25° 30′ and 23° 30′ of north latitude, where natural ice is never seen unless imported. Trenches two feet deep, dug in an open plain, are strewed over with dry straw; and in these are placed small shallow unglazed earthen pans, filled with water at sunset. The ice which is produced in them is carried away before sunrise next morning, and conveyed to an ice-cellar fifteen feet deep; where it is carefully covered with straw to be preserved from the external heat and air. A great deal, in this process, depends upon the state of the atmosphere. When calm, pure and serene, it is most favourable to the congelation; but when the winds are variable, or the weather heavy and cloudy, no ice is formed; and the same is often the case when the nights are raw and cold389.

      It was once believed that this freezing was occasioned principally by the water having been boiled; but it seems to be owing much rather to evaporation390. It is not however said that the vessels are kept continually wet on the outside, but that they are unglazed, and so porous or little burnt, that the water oozes through them; and on that account their exterior surface appears always moist391. By vessels of this kind the trouble of wetting is saved. What has been said respecting the influence of the weather serves, in some measure, to confirm my conjecture. The more it favours evaporation, the ice is not only formed more easily, but it is better; and when evaporation is prevented by the wind or the weather, no ice is produced. The latest accounts how ice is made at Benares, say expressly that boiled water is not employed; and that all those vessels, the pores of which are stopped by having been used, do not yield ice so soon or so good. In porcelain vessels none is produced; and this is the case also when the straw is wet392.

      Another method of cooling water also seems to have been known to Plutarch. It consisted in throwing into it small pebbles or plates of lead393. The author refers to the testimony of Aristotle; but this circumstance I cannot find in the works of that philosopher which have been preserved. It seems to be too unintelligible to admit of any opinion being formed upon it; and the explanation given by Plutarch conveys still less information than the proposition itself. This is the case, in general, with almost all the propositions of the ancients. We indeed learn from the questions that they were acquainted with many phænomena; but the answers scarcely ever repay the trouble which one must employ in order to understand them. They seldom contain any further illustration; and never a satisfactory explanation.

      It appears that the practice of cooling liquors, at the tables of the great, was not usual in any country besides Italy and the neighbouring states, before the end of the sixteenth century. In the middle of that century there were no ice-cellars in France; for when Bellon relates, in the Account of his travels, in 1553, how snow and ice were preserved at Constantinople throughout the whole summer, for the purpose of cooling sherbet, he assures us that the like method might be adopted by his countrymen; because he had found ice-cellars in countries warmer than France. The word glacière also is not to be met with in the older dictionaries; and it does not occur even in that of Monet, printed in 1635394. Champier, the physician who attended Francis I. when he had a conference with the emperor Charles V. and pope Paul III. at Nice, saw the Spaniards and Italians put snow, which they caused to be brought from the neighbouring mountains, into their wine in order to cool it. That practice, which excited his astonishment, he declared to be unhealthful; and this proves that in his time it had not been introduced at the French court395.

      Grand d’Aussy quotes an anecdote, related by Brantome, from which he forms the same conclusion. The dauphin, son of Francis I., being accustomed to drink a great deal of water at table, even when he was overheated, Donna Agnes Beatrix Pacheco, one of the ladies of the court, by way of precaution, sent to Portugal for earthen vessels, which would render the water cooler and more healthful; and from which all the water used at the court of Portugal was drunk. As these vessels are still used in Spain and Portugal, where the wine is cooled also with snow, both methods might have been followed in France. I have in my collection of curiosities, fragments of these Portuguese vessels; they are made of red bole; are not glazed, though they are smooth, and have a faint gloss on the surface like the Etruscan vases. They are so little burnt that one can easily break them with the teeth; and the bits readily dissolve to a paste in the mouth. If water be poured into such vessels, it penetrates their substance; so that, when in the least stirred, many air-bubbles are produced; and it at length oozes entirely through them396. The water that has stood in them acquires a taste which many consider as agreeable; and it is probable that it proceeds from the bark of the fir-tree, with which, as we read, they are burnt. When the vessels are new, they perform their service better; and they must then also have a more pleasant smell. If they really render water cold, or retain it cool, that effect, in my opinion, is to be ascribed to the evaporation. Their similarity to those in which the Indians make ice is very apparent.

      Towards the end of the sixteenth century, under the reign of Henry III., the use of snow must have been well known at the French court, though it appears that it was considered by the people as a mark of excessive and effeminate luxury. In the witty and severe satire on the voluptuous life of that sovereign and his favourites, known under the title of L’Isle des Hermaphrodites397, a work highly worthy of notice but which is exceedingly scarce, we find an order of the Hermaphrodites that large quantities of ice and snow should everywhere be preserved, in order that people might cool their liquors with them, even though they might occasion extraordinary maladies, which, it seems, were then apprehended. In the description of an entertainment we are told that snow and ice were placed upon the table before the king; and that he threw some of them into his wine; for the art of cooling it without weakening it was not then known. The same method was practised even during the whole first quarter of the seventeenth century398.

      Towards the end of the above century this luxury must have been very common in France. At that period there were a great many who dealt in snow and ice; and this was a free trade which every person might carry on. Government, however, which could never extort from the people money enough to supply the wants of an extravagant court, farmed out, towards the end of the century, a monopoly of these cooling wares. The farmers, therefore, raised the price from time to time; but the consumption and revenue decreased so much that it was not thought worth while to continue the restriction; and the trade was again rendered free. The price immediately fell; and was never raised afterwards but by mild winters or hot summers.

      The method of cooling liquors by placing them in water in which saltpetre has been dissolved, could not be known to the ancients, because they were unacquainted with that salt. They might however, have produced the same coolness by other salts which they knew, and which would have had a better effect; but this, as far as I have been able to learn, they never attempted. The above property of saltpetre was first discovered in the first half of the sixteenth century; and it was not remarked till a long period afterwards, that it belongs to other salts also.

      The Italians at any rate were the first people by whom it was employed; and about the year 1550, all the water, as well as the wine, drunk at the tables of the great and rich families at Rome, was cooled in this manner. Blasius Villafranca, a Spaniard, who practised physic in that capital, and attended many of the nobility, published, СКАЧАТЬ