[401] Centuriæ ix Memorabilium. Francof. 1599, 12mo, p. 67.
[402] De Nive, p. 38.
[403] J. B. Du Hamel, Opera Philosophica, Norimb. 1681, 4to.
[404] L. Tancredi de Fame et Siti libri tres. Ven. 1607, 4to, lib. iii.
[405] When snow or ice is mixed with salt, both begin to be liquid. This process is employed in Russia to clean windows covered with frost. They are rubbed with a sponge dipped in salt, and by these means they become immediately transparent. [The rationale of this appears to consist in the salt absorbing water and deliquescing, and in this fluid the snow subsequently dissolves, the mixture requiring a much lower temperature for its assuming the solid state.]
[406] Historia Vitæ et Mortis, § 44.—De Augmentis Scient. v. 2.—Silva Silvarum, cent. i.
[407] History of Cold, title i. 17; title v. 3; title xv. 7. [The method of making one or two freezing or cooling mixtures will not perhaps be without interest here. Where snow is not at hand, a mixture of 5 parts of powdered nitre and 5 of powdered sal-ammoniac may be mixed with 16 parts of water. This reduces the thermometer from +50° to about +10° F., or, 9 parts of phosphate of soda, 6 of nitrate of ammonia, and 4 of dilute nitric acid, reduce the thermometer from +50° to -21°; 5 parts of common salt, 5 of nitrate of ammonia and 12 of snow, reduce it from the ordinary temperature to -28°. The most intense degree of cold, probably known, has been produced by Dr. Faraday in his experiments upon the liquefaction of gases. This was effected by placing solid carbonic acid mixed with æther, under the air-pump, and exhausting.]
[408] Des Cartes Specimina Philosophiæ. Amst. 1650, 4to, p. 216.
[409] Von Hohberg says, in his Adliches Landleben, “The following, which serves more for amusement than use, is well-known to children. If one put snow and saltpetre into a jug, and place it on a table, over which water has been poured, and stir the snow and salt well round in the jug with a stick, the jug will be soon frozen to the table.” This baron, therefore, who, after he had sold his property in Austria on account of the persecution against the Protestants, wrote at Regensburg (Ratisbon), where he died in 1688, at the age of seventy-six, was not acquainted with iced delicacies. Had they been known to him, he would have certainly mentioned them where, in his Book of Cookery, he gives ample directions for laying out a table of the first rank.
[410] [The application of ice to the purposes of confectionary, has, within the last few years, become much more extensive; encouraged, no doubt, by the facility with which it is now procurable at all seasons of the year, and in any quantity. Imitations of peaches, nectarines, apricots, and other fruits, are now produced in ice paste in such perfection, as at first sight to deceive the most practised eye; and such elegances are no longer confined to the tables of the wealthy.]