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the deposition of the dissolved elements. By changes of pressure and temperature, by internal electro-chemical processes, and the specific attraction of the lateral walls (the rock traversed), sometimes lamellar deposits, and sometimes masses of concretion are produced in fissures and vesicular cavities. In this way druses and porous amygdaloids appear to have been sometimes formed. Where the deposition of the veins has taken place in parallel zones, these zones usually correspond with each other symmetrically in their nature both vertically and laterally. Senarmont has succeeded in preparing a considerable number of minerals artificially, by perfectly analogous synthetical methods.

One of my intimate friends, a highly endowed scientific observer, will, I hope, before long publish a new and important work upon the conditions of temperature of springs, and in it treat with great acumen and universality, by induction from a long series of recent observations, upon the involved phenomenon of disturbances. In the determinations of temperature made by him in Germany (on the Rhine) and in Italy (in the vicinity of Rome, in the Albanian mountains and the Apennines) from the year 1845 to 1853, Eduard Hall

59 “ Very important metalliferous lodes, perhaps the greater number, appear to have been formed by solution, while the veins filled with concretions of metal seem to be nothing but immense canals more or less obstructed, and formerly traversed by encrusting thermal waters. The formation of a great number of minerals which are met with in these lodes, does not always presuppose conditions or agents very far removed from existing causes. The two principal elements of the most widely diffused thermal waters, the alkaline sulphurets and carbonates, have enabled me to reproduce artificially, by very simple synthetic methods, 29 distinct mineral species, nearly all crystallised, belonging to the native metals (native silver, copper, and arsenic), quartz, specular iron, carbonates of iron, nickel, zinc, manganese, sulphate of baryta, pyrites, malachite, copper pyrites, sulphuret of copper, red arsenical and antimonial silver. We approach as closely as possible to the pro• cesses of nature, if we succeed in reproducing minerals in their conditions of possible association, by means of the most widely diffused natural chemical agents, and by imitating the phenomena which we still see realised in the foci in which the mineral creation has concentrated the remains of that activity which it formerly displayed with a very different energy" (H. de Šenarmont, Sur la Formation des Minéraux par la Voie Humide, in the Annales de Chemie et de Physique, 3ème série t. xxxii, 1851, p. 234 ; see also Elie de Beaumont, Sur les Emanations Volcaniques et Métallifères, in the Bulletin de la Société Géologique de France, 2e série, xv. p. 129).

mann distinguishes :-1. Purely meteorological springs, the average temperature of which is not increased by the internal heat of the earth ; 2. Meteorologico-geological springs, which, being independent of the distribution of rain, and warmer than the air, only undergo such alterations of temperature as are communicated to them by the soil through which they flow out; 3. Abnormally cold springs, which bring down their coldness from great elevations.co The more we have

60 “In order to ascertain the amount of variation of the average temperature of springs from that of the air, Dr. Eduard Hallmann observed at his former residence, Marienberg, near Boppard, on the Rhine, the temperature of the air, the amount of rain and the temperature of seven springs for five years, from the 1st December, 1845, to the 30th November, 1850; upon these observations he has founded a new elaboration of the relative temperature of springs. In this investigation the springs with a perfectly constant temperature (the purely geological springs) are excluded. On the other hand, all those springs have been made the subject of investigation which undergo an alteration in their temperature according to the seasons.

“ The variable springs fall into two natural groups :

“1. Purely meteorological springs : that is to say, those whose ave. rage is demonstrably not elevated by the heat of the earth. In these springs the amount of variation of the average from the aerial average is dependent upon the distribution of the annual amount of rain through the 12 months. These springs are on the average colder than the air when the proportion of rain for the four cold months, from December to March, amounts to more than 33} per cent.; they are on the average warmer than the air, when the proportion of rain for the four warm months, from July to October, amounts to more than 33} per cent. The negative or positive difference of the spring-average from the airaverage, is larger in proportion to the excess of rain in the above-mentioned cold or warm thirds of the year. Those springs in which the difference of the average from that of the air is in accordance with the law, that is to say, the largest possible by reason of the distribution of rain in the year, are called purely meteorological springs of undistorted average ; but those in which the amount of difference of the average from the air average is diminished by the disturbing action of the atmospheric heat during the seasons which are free from rain are called purely meteorological springs of approximate average. The approximation of the average to the aerial average is caused either by the enclo. sure, especially by a channel at the lower extremity of which the temperature of the spring was observed, or it is the consequence of a superficial course and the poverty of the feeders of the spring. In each year the amount of difference of the average from the aerial average is similar in all purely meteorological springs, but it is smaller in the approximate than in the undistorted springs, and indeed is smaller in proportion as the disturbing action of the atmospheric heat is greater. advanced of late years, by the successful employment of chemistry, in the geognostic investigation of the formation Of the springs of Marienberg 4 belong to the group of purely meteorological springs, of these 4 one is undistorted in its average, the three others are approximated in various degrees. In the first year of observation the portion of rain of the cold third predominated, and all four springs were on the average colder than the air. In the four following years of observation the rain of the warm third predominated, and in these all the four springs had a higher average temperature than the air; and the positive variation of the average of the spring from that of the air was higher, the greater the excess of rain in the warm third of one of the four years.

“ The view put forward in the year 1825, by Leopold von Buch, that the amount of variation of the average of springs from that of the air must depend upon the distribution of rain in the seasons of the year has been shown to be perfectly correct by Hallmann, at least for his place of observation, Marienberg, in the Rhenish Grauwacke mountains. The purely meteorological springs of undistorted average alone have any value for scientific climatology ; these springs are to be sought for everywhere, and to be distinguished on the one hand from the purely meteorological springs with an approximate average, and on the other from the meteorologico-geological springs.

“2. Meteorologico-geological springs: that is to say, those of which the average is demonstrably heightened by the heat of the earth. Whatever the distribution of rain may be, these springs are in their average warmer than the air, all the year round (the alterations of temperature which they exhibit in the course of the year are communicated to them by the soil through which they flow). The amount by which the average of a meteorologico-geological spring exceeds the atmospheric average, depends upon the depth to which the meteoric waters have sunk down into the interior of the earth, where the temperature is constant, before they again make their appearance in the form of a spring; this amount consequently possesses no climatological interest. The climatologist must, however, know these springs, in order that he may not mistake them for purely meteorological springs. The meteorologicogeological springs may also be approximated to the aerial average by an enclosure or channel. The springs were observed on particular fixed days, four or five times a month. The elevation above the sea, both of the place where the temperature of the air was observed, and of the different springs was carefully taken into account."

After the completion of the elaboration of his observations at Marienberg, Dr. Hallmann passed the winter of 1852—1853 in Italy, and Sound abnormally cold springs in the vicinity of ordinary ones. This is the name he gives "to those springs which demonstrably bring down cold from above. These springs are to be regarded as subterranean drains of open lakes or subterranean accumulations of water situated at a great elevation, from which the waters pour down very rapidly in fissures and clefts, and break forth at the foot of the mountain or chain of mountains in the form of springs. The idea of the abnormally

and metamorphic transformation of rocks, the greater importance has been acquired for the consideration of the waters impregnated with gases and salts which circulate in the interior of the earth, and which, when they burst forth at the surface as thermal springs, have already fulfilled the greater part of their formative, alterative, or destructive activity.

c. Vapour and Gas Springs, Salses, Mud-volcanoes,

Naphtha-fire.
(Amplification of the Picture of Nature. Cosmos,

vol. i. pp. 221–223). In the General Representation of Nature, I have shown by well ascertained examples, which, however, have not been sufficiently taken into consideration, how the salses in the various stages through which they pass, from the first eruptions accompanied by flames, to the subsequent condition of simple eruptions of mud, form as it were an intermediate step between hot springs and true volcanoes, which throw out fused earths, either in the form of disconnected cinders, or as newly formed rocks, often arranged in many beds one over the other. Like all transitions and intermediate steps both in organic and inorganic nature, the salses and mudvolcanoes deserve a more careful consideration than was bestowed upon them by the older geognosists, from the want of special knowledge of the facts.

The salses and naphtha springs are sometimes arranged in isolated close groups : like the Macalubi, near Girgenti, in Sicily, which were mentionedeven by Solinus, those near Pietra Mala, Barigazzo, and on the Monte Zibio, not far from Sassuolo in the north of Italy, or those near Turbaco in South America ; sometimes they appear to be arranged in narrow chains, and these are the most instructive and important. cold springs is, therefore, as follows:- They are too cold for the elevation at which they come forth; or, which indicates the conditions better, they come forth at too low a part of the mountain for their low temperature.” These views, which are developed in the first volume of Hallmann's Temperaturverhältnissen der Quellen, have been modified by the author in his second volume (s. 181–183), because in every meteorological spring, however superficial it may be there must be some telluric heat.

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We have long known as the outermost members of the Caucasus, in the north-west the mud-volcanoes of Taman,

61 Humboldt, Asie Centrale, t. ü, p. 58. Upon the reasons which render it probable that the Caucasus, which for ths of its length, between the Kasbegk and Elburuz, runs from E.S.E. to W.N.W. in the mean parallel of 42° 50', is the continuation of the volcanic fissure of the Asferah (Aktagh) and Thian-schan, see the work cited above, pp. 54 -61. Both the Asferah and Thian-schan oscillate between the parallels of 40° and 43°. I regard the great Aralo-Caspian depression, the surface of which, according to the accurate measurements of Struve, exceeds the area of the whole of France by nearly 107,520 geographical square miles (Op. cit. supra, pp. 309-312), as more ancient than the elevations of the Altai and Thian-schan. The fissure of elevation of the last-mentioned mountain chain has not been continued through the great depression. It is only to the west of the Caspian Sea that we again meet with it, with some alteration in its direction, as the chain of the Caucasus, but associated with trachytic and volcanic phenomena. This geognostic connection has also been recognised by Abich, and confirmed by valuable observations. In a treatise on the connection of the Thian. schan with the Caucasus by this great geognosist, which is in my possession, he says expressly :-“The frequency and decided predominance of a system of parallel dislocations and lines of elevation (nearly from east to west) distributed over the whole district (between the Black Sea and the Caspian) brings the mean axial direction of the great latitudinal central Asiatic mass-elevations, most distinctly westward from the Kosyurt and Bolar systems to the Caucasian Isthmus. The mean direction of the Caucasus, S.E.-N.W., is E.S.E.-W.N.W. in the central parts of the mountain chain, and sometimes even exactly E.-W., as in the Thian-schan. The lines of elevation which unite Ararat with the trachytic mountains Dzerlydagh and Kargabassar near Erzeroum, and in the southern parallels of which Mount Argaeus, Sepandagh, and Sabalan are arranged, constitute the most decided expression of a mean volcanic axial direction, that is to say, of the Thian-schan being prolonged westward through the Caucasus. Many other mountain-directions of Central Asia, however, also revert to this remarkable space, and stand, as elsewhere, in mutual relation to each other, so as to form vast mountain nuclei and maxima of elevation.” Pliny (vi, 17), says :-Persæ appellavere Caucasum montem Graucasim (var. Graucasum, Groucasim, Grocasum), hoc est nive candidum ;” in which Bohlen thought the Sanscrit words kâs, to shine, and gravan, rock, were to be recognised (see my Asie Centrale, t. i, p. 109). As Klausen says, in his investigations on the wanderings of Io (Rheinisches Museum für Philologie, Jahrg iii, 1845, s. 298), if the name Graucasus was corrupted into Caucasus, then a name “in which each of its first syllables gave the Greeks the idea of burning might certainly characterise a burning mountain, with which the history of the Fire-burner (Fire-igniter, a vpkaεús) would become readily and almost spontaneously associated.” It cannot be denied that myths sometimes originate from names, but the production of so great and important a fable, as the Typhonico-caucasic, can certainly not

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