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 100077 ; 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 obser-vers, may be partly owing to a slight variation in the heat of the spring itself, and partly to a difference. in the thermometers. Dr. Carrick. calculates its real temperature, as jt is drunk at the pump, at 74, 1/2 and Dr. Nott states its highest point at 76°: though we have, with a very accurate thermometer, in April, 1/98, found it to be only 72°.

According to Dr. Carrick's analysis, a gallon of 231 cubic inches contains 3O 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, 71/4 grains 5 mu-riated soda, 4, ; sulphated soda, 111/4; gelenite, 111/4 ana carbonated lime, 131/2 ; making 471/4 grains of solid contents.

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

From these investigations of the Holwell water it is evident, that the principal component parts are, a large proportion of carbonic acid gas, or fixed air ; and a certain portion of magnesia, and lime in various combinations with the muriatic, vitriolic, and carbonic acids. The general inference is, that it is considerably pure for a natural fountain, as it contains no other solid matter than is found in almost all common spring water, and in less quantity.

On account of these ingredients, especially the carbonic acid gas, the Hotwell water is efficacious in promoting salutary hemorrhages in green sickness, as well as in the blind hemorrhoids. It may be taken with advantage in obstructions and weakness of the bowels, arising from habitual costiveness. It is one of the safest and most effica-cious remedies in neutralizing and sweetening the acrimony of the vitiated humours of debilitated and consumptive patients, as it is supposed to pervade the most minute capillary vessels, and is well known to have a salutary effect on the first passages. Hence it has, for upwards of a century, been justly considered as a specific in diabetes; but if, in this disease, as well as In hectic fevers in general, the water should disagree with the stomach, as is frequently the case with per-sons who have impaired that organ by intemperance, or if their be room for the least apprehension of plethora, or a determination of the blood towards the breast and head, the use of it should not be attempted, without proper advice.

But the high reputation which this fountain has acquired, is chiefly in the cure of pulmonary consumption. From the number of unsu cessful cases, however, among those who have used the Bristol water in this disease, many have denied any peculiar efficacy in this spring, supe-rior to that of common water. Experience has proved that it alleviates some of the most distressing symptoms of this formidable disease ; and it is particularly efficacious in moderating the thirst, dry burning heat of the hands and feet, partial night-sweats, and hectical symptoms. Hence, in the earlier stages of phthisis, this water may materially contribute to the restoration of health, and even in the latter periods, mitigate the disease, when the cure is doubtful, if not hopeless.

The sensible effects of this water, when drank warm and fresh from the spring, are, a gentle glow of the stomach, succeeded sometimes by a slight and transient degree of head-ach and giddiness. By a continued use, in most cases, it is diuretic, keeps the skin moist, and perspirable, and improves the appetite and health. Its effects on the bowels are variable. On the whole, a tendency to costiveness seems to be the more general consequence of a long course of this medicinal spring, and therefore the use of a mild aperient is requisite. These, effects, however, are applicable only to invalids; tor healthy persons, who taste the water at the fountain, seldom discover any thing in it but a degree of warmth, which distinguishes it from the common element.

The season for the Hotwell is generally from the middle of May to October; but as the medicinal properties of the water continue the same throughout the year, the summer months are preferred merely on account of the concomitant benefits of air and exercise. A gentle laxative is the only necessary preparative, previous to the use of the water, especially after a journey, by which the body is generally disposed to costiveness. Two or three days rest ought to be taken after great fatigue, before this water can be used with advantage.

Early in the morning, and two hours before breakfast, is the most proper time for employing this water medicinally, when it is usual to take two glasses, spending about half an hour in gentle exercise between each dose. Two glasses are afterwards taken between break-fast and dinner; and these are generally found to be sufficient in one day. The size of the glass varies from a quarter to half a pint: the latter is reckoned a full dose.

Hectical patients, however, should begin their dietetic course with a glass of ass's milk, and gradually increase the quantity from half a pint to a pint.

Those with whom the water disagrees, when taken fasting, should begin with a quarter of a pint at a time, and take from four to six doses in the course of the day; one dose about an hour before, and another an hour after a meal.

If it operate as a cathartic, which is not uncommon in relaxed habits, a small dose of ipecacuanha, or if it occasion costiveness, a quantity of rhubarb and cream of tartar, will be necessary to assist its operation. In every case, it is best to drink it at the fountain-head, as its volatile particles easily escape. The exercise of walking, or riding on horseback, immediately after taking the water, can be recommended to the robust only ; for the inrirm require more gentle exercise, such as riding in a carriage, sailing in a boat, , and the like. Persons of a very irritable habit should sit down for a quarter of an hour, after having taken a draught of the water, which may be increased from a quarter of a pint to a pint, according to circumstances.

The Hotwell, though considerably higher than the river Avon, is, however, so far affected by the spring tides, which rise in that river, that it becomes, in some degree, turbid. It is then not thought to be so efficacious; but, after two hours pumping, the spring generally returns to its original purity.