Great curative powers have always been ascribed to certain natural sources of waters springing from the ground, and differing for the most part from ordinary sources, either by the excess or remarkable character of their constituents, or by their temperature. The savage of America, the Romans, the inhabitants of Asia, not to speak of the moderns, have all expressed in various modes their conviction of the fact. The way in which some of the more important springs have been discovered,—either by the congress of animals and their cure from various diseases (and there are more authentic narratives of the kind than that of Bladud and his swine), or by fortuitous cures in man, many of which are well authenticated,—is in itself a strong presumption in favour of the actual power of many mineral waters. But when we add to this the fact, that the chemical composition of many waters is that of very powerful medicinal agents; when we consider the effects which, on physiological principles, are likely to result from the imbibition of quantities of water well imbued with mineral principles, as well as from bathing in such waters hot or cold,—little doubt can remain as to the possession of real power by mineral waters. Add to this, that the remedy, such as it is, is generally administered with all the accessories likely to increase its beneficial action. Removal from care, good air and exercise, and improved hygienic relations, are almost always employed in conjunction with this cure.

1. The principal difficulty which we encounter at the outset of any inquiry into the nature of mineral waters is to determine what a mineral water really is. All waters, except very carefully distilled water, contain salts. Rain water, river water, and spring water, all contain salts. Malvern, one of the purest springs in England, contains about five grains of salts to the gallon. The question is, to what extent is the solution of foreign substances in a water to proceed,—or how far can it depart in other respects from the characters of ordinary water,—to entitle it to be called mineral?

Perhaps when the amount of salts and other solids held in solution in a water exceeds 60 grains in the imperial gallon it should be entitled to the term mineral. It is to be observed, that the constituents of a water which may exercise medicinal effects cannot be restricted now-a-days to the mineral or gaseous constituents of water only, seeing that a principle or congeries of substances, which exists in a great many mineral waters, of an organic vegeto-animal nature, variously termed zoogine, glairine, hargine, &c., is supposed to produce considerable effects. The extractive matters derived from the earth and from plants also contribute to the action of waters. The amount of gases, or the temperature of the water, may be sufficient to give the characters of mineral waters where the solid constituents are in very small quantities. Thus in this country the waters of Moffat and Gilsland are entitled to be called mineral, although there is nothing in the amount of salts they contain to give them this character. It is due, however, to their gaseous constituents, especially their sulphuretted hydrogen, one of the most powerful poisonous and medicinal agents, and in solution especially calculated to act upon the skin or the kidneys, and excite their secretions. On the Continent the waters of Pfeffers and Wildbad have been found by long experience to be capable of curing disease, although their mineral constituents are insignificant.

2. The most obvious division of mineral waters is into thermal and cold. Of the origin of the former many theories have been given. They probably arise from more than one source, and from various causes. The origin of thermal springs may be ascribed to the following causes:—1st, To water coming in contact with certain chemical agents in the interior of the earth; 2d, The proximity of volcanoes; 3d, The internal heat of the earth; and, 4th, To electrical changes, in which the very production of these mineral springs, and the charging of them with their various constituents, are concerned.

None of these explanations, except the last, satisfies all the conditions of the problem, and the last itself is altogether hypothetical. Against the second hypothesis it may be urged, that on the volcanic theory we cannot account for the uniform constitution of almost all thermal springs at different times and at all times; and that many hot springs occur which are neither in volcanic regions nor in the neighbourhood of volcanoes. It is an undoubted fact, proved by the phenomena observed in regard to Artesian wells, and by observations in mines, that the temperature of the earth increases as an approach is made towards the centre of the planet, in the ratio of 1° 8' of Fahrenheit for every 101 English feet. This theory of the depth may account very well for the heat of many thermal springs, but not for all; for although most thermal springs continue to preserve the same temperature, others occasionally vary, and many have been observed to undergo great changes during earthquakes. Thus Carlbad and Aix in Savoy lost temperature at the time of the earthquake at Lisbon. The electrical theory would account for almost everything, including the chemical composition of many thermal spas; since such gases as free carbonic acid and sulphuretted hydrogen are precisely the gases which we might expect to have disengaged by the chemical action of electrical currents; and the heat-producing power of electricity admits of no doubt; but what do we know concerning the currents of electricity in the interior of the earth? We must be content, then, with admitting, that of the causes of the thermaity of many mineral springs we know little with certainty. In all ages these natural hot baths, some of which issue at the temperature of boiling water, have been preferred to artificial baths. The Romans in all the conquered provinces invariably seized with avidity on these sources, and erected splendid thermes, with which nothing in modern times can compare. The admitted superior efficacy of the natural over the artificial baths has led to many conjectures as to the cause. The supposition that the specific heats of natural and artificial waters were different was refuted by a series of careful experiments performed by M. Longchamps and others. There remains the supposition, thrown out of late years, that the superior efficacy of natural thermes may be due to their electricity; but at present it is unsupported by direct experiment. Besides those springs of the temperature of the body or above it, which deserve to be called hot, as Wildbad, about 95°, Bath, 118°, there are other springs below the temperature of the body, yet hotter than ordinary water, as Buxton, 83°, and the misnamed hot wells of Bristol, only 76°.

After thermal springs come the cold, which are variously classified, according as the writer gives more or less importance to this or that predominating ingredient. Perhaps the best and most natural division is into sulphuretted, carbonated, saline, and chalybeate. The first contain large quantities of sulphuretted hydrogen gas, with or without saline ingredients. Thus Harrogate and Gilsland contain about 2 cubic inches of sulphuretted hydrogen to the pint (imperial); but the former (old well) contains 133-7 6 grains of salts in that quantity, while the latter has only 2-93. The carbonated waters are those which are highly charged with carbonic acid gas, a very valuable property, since it causes them to sit easy on the stomach. These waters, besides being grateful to the palate, possess stimulating and tonic properties. In this class of waters Britain is unfortunately entirely deficient. It is true the Leamington waters contain above 2 cubic inches of it to the pint; but this quantity is not sufficient, as it would be in the case of sulphuretted hydrogen, to give the characteristic properties. On the Continent some of the waters, Mineral Waters.

Mineral waters, as Pyrmont, are so highly charged that the gas escapes almost with explosive violence. The saline waters admit of a very important subdivision,—viz., into alkaline, muriated, and sulphated. The first are characterized by the presence of such a quantity of the carbonate of soda as to give them marked alkaline properties; in some cases, as at Vichy, these waters are thermal. In this valuable class of waters we are unfortunately deficient in this country. Their alkalinity renders them especially useful in gouty and calculous affections; and when, besides, they are thermal, they may be considered invaluable, admitting of the use of hot alkaline baths and the absorption of the curative agent through the skin, as well as of its internal administration. We have in this country waters containing trifling quantities of carbonate of soda, but nothing to give an alkaline character to the waters. Many of these waters also contain large quantities of carbonic acid. The muriated waters are those which contain large quantities of alkaline and earthy muriates or chlorides. The sulphated waters are those which contain as their chief ingredients the alkaline and earthy sulphates. Metallic sulphates, as those of iron and manganese, do also exist, but the waters then generally belong to the class of chalybeates. Chalybeate waters are those which contain iron almost always in the form of the carbonate or sulphate, in such quantity as to cause the effects of the water to be ascribed chiefly to its iron. The carbonate is generally held in solution by excess of carbonic acid. This is the reason why, on boiling such waters, a portion of the iron is precipitated, owing to the carbonic acid being driven off; and why, also, the stones in the course of chalybeate waters exhibit a red tinge, as the excess of carbonic acid with which the water was imbued flies off on exposure to the air, and the oxide of iron is precipitated. Most of the carbonated-iron waters are weak; still they produce undoubted effects. Tunbridge wells contain a very little more than the quarter of a grain in the pint. The sulphated-iron waters, again, are of a very different character, both because the ingredient itself is more powerful, and because, being exceedingly soluble, much larger quantities of it are held in solution. Very valuable waters of this class exist in Great Britain, some of them but little known. Some of these waters are too strong for use in an undiluted form, as Sandrock in the Isle of Wight, which contains no less than 41½ grains of the sulphate of iron in the pint.

Besides these classes of bodies, other substances of importance exist in mineral waters. Iodine and bromine are found occasionally in saline springs. The former element has been found so useful in scrofula and bronchocel that its presence has been considered of much consequence. Woodhall spa, in England, contains rather more than half a grain of iodine in the gallon. Arsenic of late years has been discovered in minute quantities in several waters in France and Germany; and in fact the only limit to the number of substances found in mineral waters would appear to be the extent to which the analyses are carried. Organic acids, as the acetic and formic, as well as others of a different kind, have lately been found by Scherer in the waters of Bruckenan. The principle termed zoogine or glairine, already alluded to, deserves consideration; and so much weight has been attached to it, that in artificial sulphur baths animal gelatine is sometimes substituted for it.

The analysis of mineral waters does not give the principles either as they exist in the waters, or as they are generally arranged in the published tables. For instance, in a water said to contain so much sulphate of soda and so much muriate of lime, in reality the sulphuric acid is obtained by throwing it down by means of muriatic or nitrate of baryta in the form of sulphate of baryta, from the weight of which the amount of sulphuric acid in the water is calculated. The other acids and bases are obtained by analogous methods,—the bases generally in combination with an acid, the acids with a base; and from these new compounds the amounts of acids and bases in the waters are calculated. The general rule is to give the strongest acid to the strongest base. In this way the constitution of waters is generally arrived at with considerable accuracy.

The most powerful of all mineral waters of the saline class is the sea itself. It differs somewhat in composition according to the amount of evaporation. Thus the water of the Mediterranean is more dense and saline than that of the ocean. According to the analysis of MM. Mialhe and Figuier, the water of the British Channel at Havre contains 280 grains of salts to the pint. The chief ingredients are chlorides of sodium, magnesium, and potassium, and sulphates of magnesia and lime; with a proportion of bromide of sodium. There are also other salts, traces of iodine, and probably of everything that is found soluble on the earth's surface.

3. Of the Applications of Mineral Waters, and their Use in the Cure of Disease.—Their use is external and internal. The external use of mineral waters is almost confined to the thermal waters. Here the alleged superiority of natural heat over artificial again becomes a question, several of the thermal springs being nearly pure water. How much of the superiority of these baths may be ascribed to the same causes as those which tell in favour of mineral waters generally—as change of air and scene, and improved regimen—it is most difficult to say. In speaking of the waters of Leuk in the Valais, Sir John Forbes has some excellent observations on this point in his Physician's Holiday. The springs are merely pure water, and if of ordinary temperature might be used as good drinking water. They vary in temperature from 95° to 124°. The baths are employed for many chronic diseases, but their greatest reputation is in cutaneous diseases, scrofula, chronic rheumatism, and indolent gout. The effect of such bathing is to stimulate greatly the powers of the skin, and so to cause free perspiration, thereby carrying off effete principles from the system, and causing a derivation from the internal organs, as the liver, lungs, and kidneys; increasing also the energy of the heart's action. Hence these thermal springs are chiefly employed in gout and rheumatism of a chronic character, in skin diseases, diseases of the joints, old wounds, and diseases of the bones, tumours of all kinds, and sometimes in dyspepsia. By increasing the energy of the circulation, they tend to produce absorption. In kidney diseases and in diabetes, and in chronic dropsical affections, where there is little or no disease of the heart, those springs which are sulphurated possess, in addition to their heat, a principle, sulphurated hydrogen, which, applied in this way, powerfully excites the skin, and is perhaps absorbed into the system. This class of waters is especially beneficial in skin diseases and in chronic rheumatism. Of the effect of other gases, as carburetted hydrogen, azote, and carbonic acid, in thermal springs, little is known, except that the last produces a pricking sensation on the surface of the body, which it greatly stimulates.

Among the number of external applications must be remains. It is that which gives the odour of chicken broth, or bad broth much rotted, as one writer calls it, to such waters as the Kochbrunnen at Wiesbaden. mentioned the mud baths much in use lately. The most important of these are at Franzenbad in Germany. The mineral mud of which they are prepared is found in great abundance, and is very rich in active substances. Its principal constituent parts are salts of iron, soda, lime, and alumina; it also contains umic acid in large quantity, and other vegetable matters of a gummy or resinous character. The mud is smooth and soft to the touch, and of an extremely styptic taste; heated by steam, or diluted with water, it forms a sort of cataplasm like bread crumb coloured with ink, and is used for baths or fomentations locally. From this application the best effects are said to have been derived in anaemia and chlorosis (green sickness), in old rheumatic and gouty affections, sciatica, paralysis where there is no organic disease of the spinal cord or brain, in old fractures, and in some diseases of the skin. After the surface of the body has been washed on leaving the bath, the skin is unctuous and smooth; and on taking exercise perspiration is readily induced.

Cold sulphuretted waters are sometimes heated for baths, as is practised at Harrowgate; but there is in this case much escape of the sulphuretted hydrogen. This remedy is chiefly used in skin diseases, chronic liver diseases, and chronic rheumatism. Few of the ordinary cold waters are used externally. The celebrated fountain at Ilkley in Yorkshire is merely pure cold water issuing in a full stream from the mountain, and which, applied as a douche or used as a plunge-bath, produces excessive chill, then great reaction either in the part to which it is applied or the whole surface of the body, and therefore comes under the category of simple cold baths. Besides these applications, all waters may be directed as douches to any particular part; ascending douches are used in several female complaints, and in this way carbonic and sulphuretted hydrogen gases from springs have been applied either by tubes to some particular part (carbonic acid, for example, to the ear in certain cases of deafness), or to the whole body inclosed in a suitable apparatus.

With regard to the action of cold mineral waters, it is generally either what is termed alternative or tonic. In the former case the fluids are altered in character, and this is mostly done by exciting the secretions, especially those of the skin and kidneys. The effect of this increased secretion is to remove more quickly from the system the worn-out constituents of the frame, and with them many morbid elements, and thus give fair play to the vital forces of the system, if these still retain sufficient energy to set about the work of reparation. Many of the saline waters, especially those containing alkaline sulphates and muriates, associated with sulphuretted hydrogen or without it, act powerfully on the bowels and promote the action of the liver. Of this class are Harrowgate and Cheltenham in this country, and Carlsbad abroad, which is, however, also a thermal water. Cheltenham waters contain various proportions of salts. The strongest of them, the Old Well and the Montpellier, have respectively 81-51 and 80-13 of solids to the imperial pint, being muriates and sulphates of soda, and muriates of lime and magnesia. Of the efficacy of this and similar waters in liver affections, the constant resort of sufferers from the diseases of tropical climates may be supposed to afford a proof. The saline muriated waters, many of which contain traces of iodine and bromine, besides their alternative properties, act as tonics, and are especially suited for scrofulous affections, especially if they contain iron. In many of these waters it is possible for a patient to take into the system in the course of the day a medicinal dose of the earthy muriates long ago recommended by Hygeeland as powerful remedies in scrofula; and in addition to these large quantities of muriate of soda, also a remedy in scrofula, with small quantities of bromides and iodides, whose efficacy in this class of diseases is undoubted. And it is a curious fact, that the springs in Piedmont, in which iodine was first discovered by M. Cantu, had been long renowned in scrofula; just as the ashes of burnt sponge were recognised as a remedy in goitre hundreds of years before iodine was discovered, or they were known to contain it, or M. Cointet of Geneva had demonstrated the efficacy of iodine in this disease, so common in the valleys of Switzerland and Savoy.

The virtues of chalybeate waters are popularly appreciated, and the diseases in which they are beneficial generally known. They act by strengthening the tone of the stomach, and perhaps by some chemico-vital influence in increasing the number of red particles in the blood, in which iron forms an important ingredient, and has been supposed by Liebig to perform an active part in the phenomena of respiration. Certain it is, that of all the class of tonics none equal iron in giving a healthy bloom to the complexion. The use of chalybeates is apt, however, to congest the head, and therefore they should be employed with caution where there is any tendency to such congestion. The waters containing iron are among the few requiring often some kind of medicinal preparation for their use. The bowels should be well opened previously, if possible, by some mild preparation, as the compound rhubarb pill, and their state should be attended to while the use of the water is continued. In waters containing the sulphate, alumina is often present, which makes it the more requisite to observe this caution. The dose of the sulphate should not exceed one, or at most, two grains twice a day. In those waters which contain manganese as well, it may be reckoned as so much iron. Very powerful effects indeed are often obtained from such waters, in chlorosis, anaemia, general debility, &c.

Among the prodigious list of diseases which have been supposed to be benefited by the use of mineral waters may be enumerated phthisis and chronic bronchitis. Some of the mild thermal waters, as those of Wiesbaden, taken internally, have been found beneficial in allaying pulmonary irritation in these diseases. Hot bathing in such cases is a very dangerous remedy. Chalybeate waters in incipient phthisis have been often found beneficial; but in this class of diseases, as a general rule, removal to a spa should only take place when the situation affords a favourable change in hygienic conditions. The same may be said of asthma and diseases of the heart. In diarrhoea from debility, the strong astringent ferruginous waters, especially those which contain sulphate of iron and alumina, have been found beneficial. In constipation, hypochondriasis, enlargement of the liver and spleen, biliary calculi, all the saline waters, both sulphated and muriated, thermal, or impregnated with sulphuretted hydrogen and carbonic acid gas, are useful; and in biliary calculi the alkaline waters, as those of Carlsbad and Vichy, have been found especially valuable. In catarrh of the bladder, gravel, and urinary calculi, mild thermal waters, baths of these, and alkaline saline waters, especially those of Vichy and Carlsbad, have been attended with the best results. In amenorrhoea and dysmenorrhoea, chalybeates; in the latter, thermal waters externally and internally.

1 Carlsbad waters contain a large quantity of carbonic acid, and are remarkable for the variety of their contents—manganese and iron, iodine and bromine, arsenic and boracic acid, copper, lead, tin, and antimony, are among these. Perhaps the variety of the constituents has to do with the number of diseases in which these waters are found beneficial. Two of their best ascertained beneficial effects are in cases of recently united fractures, in consolidating the callus, and in reducing enlarged livers.

2 It has been proved by the experiments of André, Gavarret, Béquerel, and others, that of 1000 parts of blood the quantity of red globules, or corpuscles, 49-6 before the use of preparations of iron, was augmented by the use of this agent to 55-7. In some cases under the use of iron the solids of the blood increased by one-half, while the water diminished in the proportion of 871 to 806.