Although his new wheel is considerably heavier than those constructed on the old plan, yet it revolves more easily on its axis; the water having a tendency to float it. Lastly, repeated exjjeriments have proved Mr. Besant's wheel to be so decidedly superior, that, when working in deep tail-water, it will carry weights in the proportion of three to one; on which account it will be particularly serviceable to tide-mills.
The extensive utility of water, for irrigating land; imparting motion to machinery; and for cold or tepid bathing, &c. is too well known to require farther explanation: we shall, therefore, confine our attention to an account of its properties when taken internally; and conclude with stating the most approved methods of preserving this salutary fluid, during long voyages; and of recovering its purity, when it has casually become corrupted or putrid.
As a constant beverage with meals, water is certainly preferable to any other liquid: nor has any case been recorded, in which the daily use of this harmless fluid has been productive of detrimental effects. Its relative salubrity, however, depends on the peculiar properties which it possesses; on the various animal, vegetable, or mineral particles, with which it may be impregnated, and the places whence it is procured. Thus, the water from Springs, being conveyed and filtred through different layers of stone, sand, &c. before it arrives at the surface of the earth, is much purer than most other waters. The transparency of that obtained from wells, varies according to the strata of earth through which it rises; but the most wholesome fluid is derived from sandy soils, where it has undergone a perfect filtration. The water of lakes and ponds, in general, has similar properties with that of rivers (see vol. iii. p. 498); but, being less agitated, it acquires a greater degree of impurity, and is consequently unfit for culinary purposes; though, on account of its softness, it may be advantageously employed in washing linen.—Rain-water collected in the vicinity of towns, of marshes, or of mines, especially during the summer, is likewise impure: it ought, therefore, to be used solely for cleaning houses, or linen, and watering gardens. The fluid, obtained by dissolving snow, is somewhat purer; and hail-water has still fewer extraneous particles, in consequence of its congealing in the air; so that it caiKiot, during its descent, combine with noxious ingredients.
As the health of mankind materially depends on the wholesomeness of the water which is introduced into the human body, by food and drink, different expedients have been devised, for preserving it in a state of purity, especially on long voyages. Hence, it has been recommended to add a small quantity of lime to every cask of water. Dr. Butler (in his Essay quoted p. 44 of the present volume), advises 4 oz. of fine, clear pearl-ash to be dissolved in 100 gallons of fresh water, and the cask to be closed in the usual manner. The proportion of the pearl-ash may be increased or diminished, according to circumstances. As an instance of its efficacy. Dr. B. relates, that he put 1 oz. of such alkali into a cask, containing 25 gallons of Thames-water, and suffered it to stand for upwards of a year and a
