Page:Willich, A. F. M. - The Domestic Encyclopædia (Vol. 1, 1802).djvu/389

Rh latter rises in a plain near a bog, and sixteen gallons of the water yield one of pure salt, which is the more remarkable, as an equal quantity cannot be obtained from less than twenty-two gallons of the waters of the German ocean.

There are several other salt-springs beside those above mentioned, particularly at a place in Durham, called Salt-water Haugh, where a multitude of saline springs rise in the river Wear, to the extent of about forty yards in length, and ten in breadth. One of these, which issues from a rock, is so strong, that in the space of a hot summer's day the surface is covered with pure crystallized salt. In these springs the water is strongest at the bottom, and richer in dry than in wet weather. They generally yield four ounces of salt from a pound of brine. It is probable that there is an immense mass of fossil salt in the bowels of the earth in the counties where these springs arise. There are several other substances dissolved in their water beside salt, particularly sulphureous matter, an impure ochre which discolours the brine, but speedily subsides; and in most, a selenitic earth is found deposited at the bottom of the salt-pans.  Brining of Corn. See.  BRISTOL HOTWELL, is situated at the bottom of St. Vincent's Rock, on the Gloucestershire bank of the river Avon, about a mile below Bristol, and within four of the Channel, or arm of the sea.

The rock, from which the hot spring issues, is a hard, compact, and very fine lime-stone, interspersed with calcareous spar, and containing those transparent quartz crystals, formerly much esteemed, and known by the name of Bristol Stones.

The Hotwell spring is a clear tepid water, which rises to the quantity of forty gallons in a minute. When fresh, it is inodorous, and sends forth numerous air bubbles if poured into a glass. It is agreeable to the palate, but without any particular taste. Its specific gravity is 1 00077; from which it is evident, that it contains but a very small intermixture of foreign substances. It is of a very moderate warmth, and the difference of temperature, as given by several observers, maybe partly owing to a slight variation in the heat of the spring itself, and partly to a difference in the thermometers. Dr. calculates its real temperature, as it is drunk at the pump, at $74 1⁄2$°; and Dr. states its highest point at 76°; though we have, with a very accurate thermometer, in April, 1798, found it to be only 72°.

According to Dr. 's analysis, a gallon of 231 cubic inches contains 30 inches of carbonic acid, and three inches of common air. By a farther analysis of Bristol water, by evaporation to dryness, he obtained the following contents in the wine gallon: of muriated magnesia, $7 1⁄4$ grains; muriated soda, 4; sulphurated soda, $11 1⁄4$; selenite, $11 3⁄4$; and carbonated lime, $13 1⁄2$; making $47 1⁄4$ grains of solid contents.

Dr., from one gallon of the water, obtained a residuum by evaporation, which weighed 52 grains. On examination, he found it to contain, in various combinations, vitriolic acid, aerial (carbonic) acid, a peculiar gas, holding calx in most intimate solution, marine salt in a large proportion, and calcareous earth. 