In regard to our knowledge of the coloring substances of mineral waters, many of which are well known to deposit red ferruginous matter, we have derived some recent very curious information from the indefatigable observer to whom we have already more than once referred, and in whose hands the microscope is revealing to us unexpected wonders. Dr. Daubeny tells us that he was assured by Professor Ehrenberg, that the red matter of some springs "is in fact composed of the outer sheaths or coverings of a multitude of little infusorial animalcules, which appear to possess the singular property of secreting oxide of iron as well as silica, and hence thrive only in chalybeate waters, which afford them the material for the coat of mail which invests their softer parts."

The efficacy of various mineral waters in the cure or relief of diseases, was not well understood, until the discovery of foreign substances which had before escaped chemical detection; but improved methods of analysis, and a knowledge of the medicinal properties of several new ingredients, have thrown much light upon their effect upon the animal economy. Some springs, for instance, had acquired a high reputation for the cure of that disgusting disease the goitre, but to what their power was to be attributed, remained involved in obscurity, until the discovery of Iodine and Bromine in their water; and to the presence of these is to be ascribed the virtues of the springs of Cheltenham, and in some degree of some in this country, as those of Balston and Saratoga. As respects the goitre, it has long been, as is well known, ascribed to the use of snow water, an opinion however in which men of science did not join; it appears from the observations of Boussingault in the Andes, that persons who habitually employ water that is devoid of its proper proportion of air, are most subject to it, while those who take the precaution to expose their water for thirty or forty hours to the air, before drinking it, escape this evil. The same traveller, according to our author, relates the extraordinary fact, "that those provinces, which are provided with salt containing iodine, are not affected with goitre, whilst in others, where the salt is destitute of that principle, the disease is endemic." Dr. Daubeny applies the fact noticed by Boussingault to the explanation of the tendency, which water that rises from calcareous rocks, has to produce goitre, which he ascribes not to its solid contents, but to the absence of the usual quantity of air. Should these views be correct, and the presence of a certain proportion of air be essential to the salubrity of water, does it not deserve the serious consi

deration of those of our medical friends who deem water which has been boiled the most salubrious, since both before, and during ebullition, a large quantity of air is expelled from it.

Dr. Daubeny goes on to speak of the methods of analyzing mineral waters, and the improvements which have been introduced into this department of chemistry; but these we have only room to recommend to the careful study of operative chemists, as well as the remarks on the manufacture of factitious mineral waters. It has been objected to the imitations of mineral waters, that they can at best be only a near approximation to the natural waters, and that we can never be absolutely sure of having a knowledge of all the contents of the latter. There are, it is true, many practical difficulties, but they have been, as in the establishment of Dr. Struve of Dresden, nearly overcome; and the difference between the genuine waters of Carlsbad, and the imitation by Dr. Struve, is so close, that it has been proved, that an individual drinking ten glasses full of the former a day, during a month, does not consume quite five grains of some of the ingredients which are present in them in the smallest proportions detected by analysis, and which are of the least, if of any efficacy. There seems to be no good reason, then, why an artificial mineral water, made upon strict chemical principles, should not possess all the virtues of the original.

One of the most remarkable mineral waters is found in the valley of the Furnas, in one of the Azores, rising by innumerable orifices from the soil, and running out from the sides of the valley. It belongs to the class of alkaline waters, and was noticed by the late Dr. Turner of London, to whom portions of it were sent by Lord Napier. Its analysis affords silicic acid, carbonates of iron, magnesia, lime, and soda, with chloride of sodium, and an abundance of carbonic acid gas. Dr. Turner has communicated an account of it to the Royal Society of Edinburgh. It has decided alkaline reaction, is of an agreeable taste, and is peculiarly efficacious in affections of the stomach and digestive organs. During the summer, hundreds resort to the valley for the purpose of drinking this salubrious water; and the most beneficial results have followed its use, to the dyspeptic and debilitated. It is now imported into England, and is taking the place of the famous Seltzer water; and has recently, we perceive, been introduced into this country.

In the course of this memoir, Dr. Daubeny notices the occurrence of salt springs, and the theory that attributes their origin to beds of salt, or of muriatiferous clays, produced by

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evaporation of sea water, or of salt lakes. He thinks that, in many cases, there may be reason to suppose that volcanic heat has caused their deposition, and that the presence of the sulphate of lime and other bases, which is so generally observed in such deposits, may have been due to the sulphuretted hydrogen, which is at the present day an ordinary effect of volcanic processes. Mr. Lyell* has, with great ingenuity, endeavored to explain the origin of rock salt from salt water, and has attempted to show how the deposition of salt may be going on at the present time, in the Mediterranean, from which the evaporation is very copious and rapid. The surface water, he supposes, becomes impregnated with a slight excess of salt-has its specific gravity increased, and falls in consequence to the bottom-while lighter water rises to the top, or is introduced by rivers, and by the current from the Atlantic. He supposes that the heavier fluid flows on till it reaches the lowest part of one of the submarine basins, into which the bottom of this sea is supposed to be divided. In this manner, additions are constantly making to the brine, until the lower portions are fully saturated, and the salt begins to be precipitated, and continuous beds of pure rock salt-hundreds of miles in length-like those in the mountains of Poland, Hungary, &c. may be formed. To this theory, Dr. Daubeny objects the want of a more efficient means for bringing about 2 separation of the solid contents of the water, than evaporation; and this he finds in volcanic action—" a submarine volcano, or any other independent cause, producing a high temperature in any part of the bed of the ocean, might supply this desideratum; it would separate the salt from that portion of the water which came most within its immediate influence, converting the fluid into vapor, which, in a highly compressed condition, we may imagine to be interposed between the bed of salt in the act of forming, and the body of the superincumbent ocean." These views our ingenious author has strengthened by the geological observations of others; and in the narrative of his excursion to the Lake Amsanctus, he has traced the connexion between the operations of volcanoes, the emanations of carbonic acid, and the formation of beds of rock salt, and the association of salt springs-as in Tuscany and Sicily-with gypsum and sulphur. "Their occurrence in such localities as these, might induce us to conjecture that the same volcanic action which produced the sulphuric salts, and volatilized the sul

* Principles of Geology, 1. 297.

phur-has been instrumental, also, in separating the salt from its solution in water, and thus serve to explain, in these instances at least, the puzzling fact, that rock salt is found associated, as is so commonly the case, with beds of gypsum." The connexion between these phenomena, is placed in a clearer view by the following tabular arrangement :

Although it may perhaps be doubted if we shall ever arrive at a perfectly satisfactory solution of all the phenomena connected with the geological structure of the earth, we have still an inviting and extended field before us, and every inducement to persevere. There are many appearances of rocks and strata, of the connexion and influence of stratified and unstratified masses, but imperfectly comprehended. The volcanic or non-volcanic origin of many parts of the earth's surface is yet involved in obscurity, the elevation or subsidence of many strata is as yet undecided, and upon these and many other topics in this interesting science, the more careful and correct examination of volcanic countries may be expected to throw much light. Valuable results we think are to be anticipated from the electrical researches that are going on, especially from those in which electricity and magnetism are both concerned. Such are those which have been already obtained by Mr. Fox, in the mines of Cornwall. The agency which galvanism has been shown to have upon the formation or development of crystals and mineral masses, is opening to the geologist encouraging prospects, and pointing to agents whose influence may be found to have been hitherto too much overlooked.

If in the organic remains of a former world we see proofs of design, adaptations, contrivances, and mechanisms adapted to the production of certain ends—so do we, in the disturbing forces that have been and are instrumental in causing the earthquake and volcano. Nor will the careful study of volcanic geology be found wanting in those valuable lessons, which the eloquence of a Buckland has drawn from that of fossils; and we shall learn to appreciate both, as but parts "of that system of wise and benevolent contrivances, prospectively subsidiary to the wants and comforts of the future inhabitants of the globe; and extending onwards from its first formation, through the subsequent revolutions and convulsions that have affected the surface of our planet."*

The narrative mentioned at the head of this article has claims, as we have hinted, upon the attention of the classical scholar; it will also be found interesting to the naturalist and lover of picturesque scenery. It describes a portion of Apulia, which, if not rarely visited, has been rarely described by travellers. A part of the road, however, as stated by our author, was described by Mr. Fuller Craven, in his tour through the southern provinces of the Kingdom of Naples; but he appears to have omitted to notice the two most interesting points, namely, the Lake Ansanto, and the extinct volcanoes of Mount Vultur. Sir R. Colt Hoare, in his classical tour, in which he intended to supply the blanks that existed in the descriptions of the interior of Italy, was prevented, as stated by Dr. Daubeny, by the inclemency of the season, from proceeding further on the road to Apulia, than Benevento.

Not only do many interesting and instructive geological objects present themselves in this part of Italy, but, as observed by our author, the tour may readily comprehend the classical country of the Samnites and the Hirpini-the birth-place of Horace, and the field of Cannæ. On the third of December, Dr. Daubeny left Naples, proceeding along a level plain, which, in the vicinity of Naples, is marshy and unwholesome. The country, however, as he advanced, became more fertile, and though in the midst of winter, "it was easy to imagine the luxuriance which it must present in autumn, when the elms and poplars, which extend along the whole of this great plain to the very foot of the Apennines, continue in full verdure, and are united by festoons of vines, stretching from tree to tree, and loaded with a profusion of fruit."

* Buckland.