half, opening it once in 4 months; when he found it perfectly sweet. He adds, that he afterwards used some of this preserved fluid for boiling Pease and Burgoo; that it made the former as soft, and answered the different culinary purposes as well, as water newly drawn from rivers.
In the first volume of the "Rapport General des Travaux de la Societé Philomatique de Paris," we meet with a Memoir by M. Vauquelin, on several means of preserving water, on long voyages.—With this view, the inside of the casks was washed with lime-water, which changed into a calcareous carbonate, and thus effectually prevented putrefaction. The same desirable object may be attained, by adding a small portion of vitriolic acid and of alkali, to every cask; which will preserve the water in a pure and salubrious state, for at least 12 months. Charcoal has also proved to be eminently adapted to such purpose: the most advantageous mocle of employing this substance, is that of charring the inner surface of the staves, previously to constructing the casks.
The latest method of preserving fresh water in a sweet state, at a great distance from land, is that communicated to the Society for the Encouragement of Arts, &c. in 1800, by Samuel Bentham, Esq. and for which he was presented with their gold medal. It consists simply in stowing water in wooden cases or tanks, lined with metallic plates, known under the name of tinned copper-sheets; the joinings of such cases being carefully soldered, so that the water cannot find the least access to the wood. These tanks may be manufactured of any shape adapted to the hold of the ship, and thus contain any quantity of water; so that considerable stowage-room may be saved on board of vessels, which is at present occupied by the casks.—In justice to Mr. Bentham we add, that two tanks of water thus preserved, were submitted to the examination of the Society; and, though they had been three years and a half at sea, the fluid was perfectly sweet, wholesome, and fit for any culinary purpose.
On the other hand, if water has become putrid, it may be divested of its pernicious properties, by the process recommended, vol. i. p. 37; by boiling, or by distillation; and by filtering it through the machines delineated and described in the article Filtration; or through Mr. Collier's patent vessels for purifying oil and other liquids; a specification of which is given in the 10th vol. of the "Repertory of Arts," &c. and illustrated with a Plate.
In October, 1790, a patent was granted to Mrs. Johanna Hempel, for her invention of a composition; which, on being formed into vessels, is said to possess the advantage of filtering water or other liquids, in a cheaper, more easy, and expeditious manner, than could be effected by any other preparation. The proportions of the materials, employed for this purpose, vary according to the size of the basons, or jars to be manufactured. Thus, for vessels intended to contain a quantity of water not exceeding one gallon, four parts of tobacco-pipe clay must be incorporated with nine parts of coarse sea, river, drift, or pit-sand, and worked on a potter's-wheel into any form, as fancy or convenience may direct. But, as the composition thus prepared, is
