This disquisition we have been led into from the first class of waters; and we may now add, that chemistry may probably detect ingredients not yet suspected in some of these, as azotic gas appears to have been found in those of Buxton; and perhaps oxygen may occur in others, as it has been suspected in the waters of Plombieres. The second class, the acidulous waters, stimulate the stomach and improve the appetite. They are certainly refrigerant and antiseptic: refrigerants we shall find to be deobstruent, and, in some constitutions, diuretic. Perhaps the acidulous waters are adapted to those who have injured the stomach by excess in drinking: when joined with chalybeates, this advantage is more strikingly conspicuous. If ever these waters prove peculiarly useful as deobstruents, it is when they are united with neutral salts; but to follow this subject would be to anticipate what more naturally occurs under the next head.

The saline waters are certainly cathartic and diuretic: have the credit of being alterants and deobstruents. Of the supposed acrimonies of the fluids we have already spoken, (see Alterants,") and have remarked, that though what appears in excrementitious fluids must have existed in the blood, yet it never formally appears in that fluid. We may now add, that such is the connection between the secretory organs, that a derivation-from one of these will prevent a deposition on some others. Thus the discharge of the more fluid secretions from the bowels will check similar ones of the saliva and of the skin; and to cure, or certainly to prevent, the recurrence of cutaneous eruptions, there is no more certain remedy than the saline mineral waters, particularly sea water. Obstructions of greater conse-ice occur in the chylopoietic viscera and the conglobate glands. Dissection shows us that the liver, the pancreas, and other organs of the abdomen, may be obstructed, enlarged, become scirrhous, or otherwise diseased. For these complaints the saline mineral waters are recommended with advantage. To explain their effects we must first notice the general principle previously alluded to, that the chief and first effect of all deobstruents is refrigerant or sedative. When obstruction exists, if the circulation is accelerated and the obstacle is not conquered, the matter must be more firmly impacted; and at a distance from the source of power, the action of the vessels must be comparatively weak and inconsiderable. To this we know but of one exception, viz. the action of mercurials, whose stimulant power is chiefly felt in the extreme vessels. Independent, however, of the refrigerant effect of saline medicinal waters, they generally increase the discharge from the excretory ducts of the obstructed part, and of course relieve the over distended vessels; not only preventing further impaction, but taking away the impediments to the action of arteries already obstructed.

The action of these waters on obstructions of the lymphatic glands we have also already glanced at. It was the language of Dr. Cullen that saline waters, particularly sea water,' washed out' the lymphatic system. We know not, however, by what channels they could reach glands whose disease consisted in refusing a passage to every absorbed fluid; and when we before noticed this effect, and was willing to attribute it to the power which salts possess of rendering the gluten more fluid, we were obliged to allow that the matter of scrofulous glands was not gluten. Saline waters are, however, very valuable remedies in these complaints; and they seem useful by increasing the action of the lymphatic system, which is probably in this disease defective. Obstructions of the mesenteric glands are very often relieved by saline waters; and from what we have observed of their powers, it will be easy to see on what principle their good effects depend. In some late authors, the physconia abdominalis is mentioned among the diseases to which these waters are adapted. The complaint consists in hardened tumours in the abdomen. apparently not connected with glands of either system: and if the remedy is useful, we must confess our ignorance of its manner of acting.

Some of these saline waters are recommended in cases where we hesitate respecting their power, or the means, if their efficacy be admitted, by which they relieve. We allude to those cases of exhausted constitutions which are supposed to find relief from Cheltenham. It is said that the chalybeate impregnation obviates the debilitating power of the cathartic salts. In fact, we strongly suspect that in all such cases an obstruction of the liver has occasioned or coincided with the other complaints, and that the relief obtained has followed from the effects of the waters formerly mentioned. It is contended, however, that they are useful in other circumstances, and we cannot deny that they have appeared to be so; but with the little experience we at a distance can possess, it would be the height of arrogance to contend against the enlarged field of observation a residence on the spot affords.

Melancholy and dropsy, two diseases for which the saline waters are recommended, need not detain us: in each there are generally obstructions in the viscera, and in each gentle laxatives are useful.

The aerated alkalinewaters are now peculiarly fashionable, and the artificial soda water, which we shall mention in another article, is frequently drunk: it is recommended as a stimulant, a tonic, a solvent, and a stomachic. In weak digestions, in gouty apepsia, in stomachs abounding with acid, it is highly commended, and is not without its merit, though the popularis aura seem to have extolled it beyond its bearing. In nephri-- tic and calculous complaints it is recommended as a solvent; but it is doubtful whether its power is obvious in any other organ except the stomach. The acid evolved in the urea, in the perspiration and calculi of arthritic patients, is apparently generated in the stomach, and is there counteracted by antacids. If, howy ever the alkali can be conveyed without change to the bladder, it may certainly be useful as a solvent. In inflammatory fevers it acts as a cooling laxative, and in some cases of hectic appears beneficial; but, as a remedy in putrid fevers, this gas is too trifling as an antiseptic to detain us a moment.