greater than those to which human labour has been enabled to penetrate. We are able to give in numbers the depth of the shaft where the strata of coal, after penetrating a certain way, rise again at a distance that admits of being accurately defined by measurements. These dips show that the carboniferous strata, together with the fossil organic remains which

bühel reached England at an early period, for I find it remarked in Gilbert, de Magnete, that men have penetrated 2400 or even 3000 feet into the crust of the earth. ("Exigua videtur terræ portio, quæ unquam hominibus spectanda emerget aut eruitur; cum profundius in ejus viscera, ultra efflorescentis extremitatis corruptelam, aut propter aquas in magnis fodinis, tanquam per venas scaturientes aut propter aeris salubrioris ad vitam ope rariorum sustinendam necessarii defectum, aut propter ingentes sumptus ad tantos labores exantlandos, multasque difficultates, ad profundiores terræ partes penetrare non possumus; adeo ut quadringentas aut [quod rarissime] quingentas orgyas in quibusdam metallis descendisse, stupendus omnibus videatur conatus." Gulielmi Gilberti, Colcestrensis, de Magnete Physiologia nova. Lond., 1600, p. 40.)

The absolute depth of the mines in the Saxon Erzgebirge, near Freiburg, are in the Thurmhofer mines, 1944 feet; in the Honenbirker mines, 1827 feet; the relative depths are only 677 and 277 feet, if, in order to calculate the elevation of the mine's mouth above the level of the sea, we regard the elevation of Freiburg as determined by Reich's recent observations to be 1269 feet. The absolute depth of the celebrated mine of Joachimsthal in Bohemia (Verkreuzung des Jung Hauer Zechen-und Andreasganges), is full 2120 feet; so that, as Von Dechen's measurements show that its surface is about 2388 feet above the level of the sea, it follows that the excavations have not as yet reached that point. In the Harz, the Samson mine at Andreasberg, has an absolute depth of 2197 feet. In what was formerly Spanish America, I know of no mine deeper than the Valenciana, near Guanaxuato (Mexico), where I found the absolute depth of the Planes de San Bernardo to be 1686 feet; but these planes are 5960 feet above the level of the sea. If we compare the depth of the old Kuttenberger mine (a depth greater than the height of our Brocken, and only 200 feet less than that of Vesuvius) with the loftiest structures that the hands of man have erected, (with the Pyramid of Cheops and with the Cathedral of Strasburg,) we find that they stand in the ratio of eight to one. In this note I have collected all the certain information I could find regarding the greatest absolute and relative depths of mines and borings. In descending eastward from Jerusalem, towards the Dead Sea, a view presents itself to the eye, which, according to our present hypsometrical knowledge of the surface of our planet, is unrivalled in any country; as we approach the open ravine through which the Jordan takes its course, we tread, with the open sky above us, on rocks which, according to the barometric measurements of Berton and Russegger, are 1385 feet below the level of the Mediterranean. (Humboldt, Asie Centrale, th. ii. p. 323.)

they contain, must lie, as, for instance, in Belgium, more than five or six thousand feet* below the present level of the sea; and that the calcareous and the curved strata of the Devonian basin penetrate twice that depth. If we compare these subterranean basins with the summits of mountains that have hitherto been considered as the most elevated portions of the 'raised crust of the Earth, we obtain a distance of 37,000 feet (about seven miles), that is about theth of the Earth's radius. These, therefore, would be the limits of vertical depth and of the superposition of mineral strata, to which geognostical inquiry could penetrate, even if the general elevation of the upper surface of the earth were equal to the height of the Dhawalagiri in the Himalaya, or of the Sorata in Bolivia. All that lies at a greater depth below the level of the sea than the shafts or the basins of which I have spoken, the limits to which man's labours have penetrated, or than the depths to which the sea has in some few instances been sounded, (Sir James Ross was unable to find bottom with 27,600 feet of line,) is as much unknown to us as the interior of the other

*Basin-shaped curved strata, which dip and reappear at measureable distances, although their deepest portions are beyond the reach of the miner, afford sensible evidence of the nature of the earth's crust at great depths below its surface. Testimony of this kind possesses, consequently, a great geognostic interest. I am indebted to that excellent geognosist, Von Dechen, for the following observations. "The depth of the coal-basin of Liege, at Mont St. Gilles, which I, in conjunction with our friend Von Oeynhausen, have ascertained to be 3890 feet below the surface, extends 3464 feet below the surface of the sea, for the absolute height of Mont St. Gilles certainly does not much exceed 400 feet; the coal-basin of Mons is fully 1865 feet deeper. But all these depths are trifling compared with those which are presented by the coal-strata of Saar-Revier (Saarbrücken). I have found, after repeated examinations, that the lowest coal-stratum which is known in the neighbourhood of Duttweiler, near Bettingen, north-east of Saarlouis, must descend to depths of 20,682 and 22,015 feet (or 3.6 geographical miles) below the level of the sea." This result exceeds, by more than 8000 feet, the assumption made in the text regarding the basin of the Devonian strata. This coal-field is therefore sunk as far below the surface of the sea, as Chimborazo is elevated above it: at a depth at which the earth's temperature must be as high as 435° F. Hence, from the highest pinnacles of the Himalaya to the lowest basins containing the vegetation of an earlier world, there is a vertical distance of about 48,000 feet, or of the 435th part of the Earth's radius.

planets of our solar system. We only know the mass of the whole Earth and its mean density by comparing it with the open strata, which alone are accessible to us. In the interior

of the Earth, where all knowledge of its chemical and mineralogical character fails, we are again limited to as pure conjecture, as in the remotest bodies that revolve round the Sun. We can determine nothing with certainty regarding the depth at which the geological strata must be supposed to be in state of softening or of liquid fusion, of the cavities occupied by elastic vapour, of the condition of fluids when heated under an enormous pressure, or of the law of the increase of density from the upper surface to the centre of the Earth.

*

The consideration of the increase of heat with the increase of depth towards the interior of our planet and of the reaction of the interior on the external crust leads us to the long series of volcanic phenomena. These elastic forces are manifested in earthquakes, eruptions of gas, hot wells, mud volcanoes and lava currents from craters of eruptions, and even in producing alterations in the level of the sea. Large plains and variously indented continents, are raised or sunk, lands are separated from seas, and the ocean itself, which is permeated by hot and cold currents, coagulates at both poles, converting water into dense masses of rock, which are either stratified and fixed, or broken up into floating banks. The boundaries of sea and land, of fluids and solids, are thus variously and frequently changed. Plains have undergone oscillatory movements, being alternately elevated and depressed. After the elevation of continents, mountain-chains were raised upon long fissures, mostly parallel, and, in that case, probably contemporaneous; and salt lakes and inland seas, long inhabited by the same creatures, were forcibly separated; the fossil remains of shells and zoophytes still giving evidence of their original connexion. Thus, in following phenomena in their mutual dependence, we are led from the consideration of the forces acting in the interior of the Earth, to those which cause eruptions on its surface, and by the pressure of elastic vapours, give rise to burning streams of lava that flow from open fissures.

* [See Daubeney On Volcanoes, 2nd edit. 1848, p. 539, &c., on the so-called mud volcanoes, and the reasons advanced in favour of adopting the term "salses" to designate these phenomena.]-Tr.

The same powers that raised the chains of the Andes and the Himalaya to the regions of perpetual snow, have occasioned new compositions and new textures in the rocky masses, and have altered the strata which had been previously deposited from fluids impregnated with organic substances. We here trace the series of formations, divided and superposed according to their age, and depending upon the changes of configuration of the surface, the dynamic relations of upheaving forces, and the chemical action of vapours issuing from the fissures.

The form and distribution of continents, that is to say, of that solid portion of the Earth's surface which is suited to the luxurious development of vegetable life, are associated by intimate connexion and reciprocal action with the encircling sea, in which organic life is almost entirely limited to the animal world. The liquid element is again covered by the atmosphere, an aerial ocean in which the mountain-chains and high plains of the dry land rise like shoals, occasioning a variety of currents and changes of temperature, collecting vapour from the region of clouds, and distributing life and motion by the action of the streams of water which flow from their declivities.

Whilst the geography of plants and animals depends on these intricate relations of the distribution of sea and land, the configuration of the surface, and the direction of isothermal lines (or zones of equal mean annual heat), we find that the case is totally different when we consider the human race—the last and noblest subject in a physical description of the globe. The characteristic differences in races, and their relative numerical distribution over the Earth's surface, are conditions affected not by natural relations alone, but at the same time and specially, by the progress of civilization, and by moral and intellectual cultivation, on which depends the political superiority that distinguishes national progress. Some few races, clinging, as it were, to the soil, are supplanted and ruined by the dangerous vicinity of others more civilized than themselves, until scarce a trace of their existence remains. Other races, again, not the strongest in numbers, traverse the liquid element, and thus become the first to acquire, although late, a geographical knowledge of at least the maritime lands of the whole surface of our globe, from pole to pole.

I have thus, before we enter on the individual characters of

that portion of the delineation of nature which includes the sphere of telluric phenomena, shown generally in what manner the consideration of the form of the Earth and the incessant action of electro-magnetism and subterranean heat may enable us to embrace in one view the relations of horizontal expan sion and elevation on the Earth's surface, the geognostic type of formations, the domain of the ocean, (of the liquid portions of the Earth,) the atmosphere with its meteorological processes, the geographical distribution of plants and animals, and finally, the physical gradations of the human race, which is, exclusively and everywhere, susceptible of intellectual culture. This unity of contemplation presupposes a connexion of phenomena according to their internal combination. A mere tabular arrangement of these facts would not fulfil the object I have proposed to myself, and would not satisfy that requirement for cosmical presentation awakened in me by the aspect of nature in my journeyings by sea and land, by the careful study of forms and forces, and by a vivid impression of the unity of nature in the midst of the most varied portions of the Earth. In the rapid advance of all branches of physical science much that is deficient in this attempt will, perhaps, at no remote period, be corrected, and rendered more perfect, for it belongs to the history of the development of knowledge that portions which have long stood isolated become gradually connected, and subject to higher laws. I only indicate the empirical path, in which I and many others of similar pursuits with myself, are advancing, full of expectation that, as Plato tells us Socrates once desired, "Nature may be interpreted by reason alone.”*

The delineation of the principal characteristics of telluric phenomena must begin with the form of our planet, and its relations in space. Here, too, we may say that it is not only the mineralogical character of rocks, whether they are crystalline, granular, or densely-fossiliferous, but the geometrical form of the Earth itself which indicates the mode of its origin, and is, in fact, its history. An elliptical spheroid of revolution gives evidence of having once been a soft or fluid mass. Thus, the Earth's compression constitutes one of the most

*Plato, Phado, p. 97. (Arist. Metaph., p. 985.) Compare Hegel, Philosophie der Geschichte, 1840, s. 16.