Bekker), and of a spontaneous incentive to motion. This kind of mental comprehension which I have named intuition, together with that felicitous acumen in the power of combining his ideas, which was so characteristic of the Stagyrite, led him to the assumption of an apparent transition from the inanimate to the living, from the mere element to the plant, and induced him even to adopt the view that in the ever ascending processes of plastic formation there were gradual and intermediate stages connecting plants with the lower animals (Aristot. de part. Animal. iv, 5, p. 681, a 12, and hist. Animal. viii, 1, p. 588, a 4, Bekker). The history of organisms (taking the word history in its original sense, and therefore in relation to the faunas and floras of earlier periods of time) is so intimately connected with geology, with the order of succession of the superimposed terrestrial strata and with the chronometrical annals of the upheaval of continents and mountains; that it has appeared most appropriate to me, on account of the connection of great and widely diffused phenomena, to avoid establishing the natural division of organic and inorganic terrestrial life as the main element of classification in a work treating of the Cosmos. We are not here striving to give a mere morphological representation of the organic world, but rather to arrive at bold and comprehensive views of nature, and the forces which she brings into play.

I.

Size, Configuration, and Density of the Earth.-The Heat in the interior of the Earth, and its distribution.—Magnetic Activity, manifested in changes of Inclination, Declination, and Intensity of the force under the influence of the Sun's position in reference to the Heat and Rarefaction of the Air.-Magnetic Storms.-Polar Light.

That which in all languages is comprehended under etymologically differing symbolical forms by the expression Nature, and which man, who originally refers everything

to his own local habitation, has further designated as Terrestrial Nature is the result of the silent co-operation of a system of active forces, whose existence we can only recognise by means of that which they move, blend together, and again dissever; and which they in part develope into organic tissues (living organisms), which have the power of re-producing like structures. The appreciation of nature is excited in the susceptible mind of man through the profound impression awakened by the manifestation of these forces. Our attention is at first attracted by the relations of size in space exhibited by our planet, which seems only like a handful of conglomerated matter in the immeasurable universe. A system of co-operating forces, which either tend to combine or separate (through polar influences), shows the dependence of every part of nature upon other parts, both in the elementary processes (as in the formation of inorganic substances), and in the production and maintenance of life. The size and form of the earth, its mass, that is to say, the quantity of its material parts, which when compared with the volume determines its density, and by means of the latter, under certain conditions, both the constitution of the interior of the earth and the amount of its attraction, are relations which stand in a more manifest, and a more mathematically demonstrable dependence upon one another than we observe in the case of the above named vital processes, in the distribution of heat, in the telluric conditions of electro-magnetism, or in the chemical metamorphoses of matter. Conditions, which we are not yet able to determine quantitatively on account of a complication of phenomena, may nevertheless be present, and may be demonstrated through inductive reasoning.

Although the two kinds of attraction, namely, that which acts at perceptible distances, as the force of gravity (the gravitation of the celestial bodies towards one another), and that which is manifested at immeasurably small distances, as molecular or contact-attraction, cannot in the present condition of science be reduced to one and the same law, yet it is not on that account the less credible that capillary attraction and endosmosis, which is so important in reference to the ascent of fluids, and in respect to animal and vegetable physiology, may be quite as much affected by the force of gra

vitation and its local distribution as electro-magnetic processes and the chemical metamorphosis of matter. To refer to extreme conditions, we may assume that if our planet had only the mass of the moon, and therefore almost six times less intensity of gravity, the meteorological processes, the climate, the hypsometrical relations of upheaved mountain chains and the physiognomy of the vegetation would be quite different from what they now are. The absolute size of our planet which we are here considering, maintains its importance in the collective economy of nature merely by the relations which it bears to mass and rotation; for even in the universe, if the dimensions of the planets, the quantitative admixture of the bodies which compose them, their velocities and distances from one another, were all to increase or diminish in one and the same proportion, all the phenomena depending upon relations of gravitation would remain unchanged in this ideal macrocosmos, or microcosmos.2

a. Size, Figure, Ellipticity, and Density of the Earth. (Expansion of the Picture of Nature, Cosmos, vol. i, pp. 154-164.)

The earth has been measured and weighed in order to determine its form, density, and mass. The accuracy which has been incessantly aimed at in these terrestrial determinations, has contributed, simultaneously with the solution of the problems of astronomy, to improve instruments of measurement, and methods of analysis. A very important part

2 "The law of reciprocal attraction which acts inversely as the square of the distance is that of emanations, proceeding from a centre. It appears to be the law of all those forces, whose action is perceptible at sensible distances, as in the case of electrical and magnetic forces. One of the remarkable properties of this law is that, if the dimensions of all the bodies in the universe, together with their mutual distances and their velocities, were proportionally increased or diminished, they would still describe curves precisely similar to those which they now describe; so that the universe, after being thus successively reduced to the smallest conceivable limits, would still always present the same appearance to the observer. These appearances are consequently independent of the dimensions of the universe, as in virtue of the law of the ratio which exists between force and velocity, they are independent of absolute movement in space."-Laplace, Exposition du Syst. du Monde (5ème éd.), p. 385,

of the process involved in the measurement of a degree is strictly astronomical, since the altitudes of stars determine the curvature of the arc, whose length is found by the solution of a series of triangles. The higher departments of mathematics have succeeded, from given numerical data, in solving the difficult problems of the figure of the earth, and the surface of equilibrium of a fluid homogeneous, or dense shell-like heterogeneous mass, which rotates uniformly round a solid axis. Since the time of Newton and Huygens, the most distinguished geometricians of the eighteenth century have devoted themselves to the solution of these problems. It is well that we should bear in mind that all the great results which have been attained by intellectual labour and by mathematical combinations of ideas, derive their importance not only from that which they have discovered and which has been appropriated by science, but more especially from the influence which they have exerted on the development and improvement of analytical methods.

"The geometrical figure of the earth, in contradistinction to the physical, determines the surface which the superficies of water would assume in passing through a net-work of canals, connected with the ocean, and covering and intersecting the earth in every direction. The geometrical surface intersects the directions of the forces vertically, and these forces are composed of all the attractions emanating from the individual particles of the earth, combined with the centrifugal force, which corresponds with its velocity of rotation. This surface must be generally considered as approximating very closely to an oblate spheroid, for irregularities in the distribution of the masses in the interior of the earth will also, where the local density is altered, give rise to irregularity in the geometrical surface, which is the product of the co-operation of unequally distributed elements. The physical surface is the direct product of the surface of

3 Gauss, Bestimmung des Breitenunterschiedes zwischen den Sternwarten von Göttingen und Altona, 1828, s. 73. (These two observatories, by a singular chance, are situated within a few yards of the same meridian.)

4 Bessel, Ueber den Einfluss der Unregelmässigkeiten der Figur der Erde auf geodätische Arbeiten und ihre Vergleichung mit astronomischen Bestimmungen, in Schumacher's Astron. Nachr. Bd. xiv, No. 329, s. 270, and Bessel and Baeyer, Gradmessung in Ostpreussen, 1838, s. 427-442.

the solid and fluid matter on the outer crust of the earth." Although while it is not improbable, judging from geological data, that the incidental alterations which are readily brought about in the fused portions of the interior of the earth, when they are moved by a change of position of the masses, may even modify the geometrical surface by producing curvature of the meridians and parallels in small spaces, and at very widely separated periods of time; the physical surface of the oceanic parts of our globe is periodically subjected to a change of place in the masses, occasioned by the ebbing and flowing (or in other words the local depression and elevation) of the fluid element. The inconsiderable amount of the effects of gravity in continental regions may indeed render a gradual change inappreciable to actual observation; and according to Bessel's calculation, in order to increase the latitude of a place by a change of only 1", it must be assumed that there is a transposition in the interior of the earth of a mass, whose weight (its density being assumed to be that of the mean density of the earth) is that of 7296 geographical cubic miles. However large the volume of this transposed mass may appear to us when we compare it with the volume of Mont Blanc, or Chimborazo, or Kintschindjinga, our surprise at the magnitude of the phenomenon soon diminishes when we remember that our terrestrial spheroid comprises upwards of 1696 hundreds of millions of such cubic miles.

5

Three different methods have been attempted although with unequal success for solving the problem of the figure of the earth whose connection with the geological question of the earlier liquid condition of the rotating planetary bodies was known at the brilliant epoch of Newton, Huygens and Hooke. These methods were the geodetico-astro

5 Bessel, Ueber den Einfluss der Veränderungen des Erdkörpers auf die Polhöhen, in Lindenau und Bohnenberger, Zeitschrift für Astronomie. Bd. v, 1818, s. 29. "The weight of the earth, expressed in German pounds=9933 × 10.21, and that of the transposed mass = 947 × 10.14."

6 The theoretical labours of that time were followed by those of Maclaurin, Clairaut, and d'Alembert, by Legendre and by Laplace. To this latter period we may add the theorem advanced by Jacobi, in 1834, that ellipsoids of three unequal axes may, under certain conditions, represent the figures of equilibrium no less than the two previouslyindicated ellipsoids of rotation.-See the treatise of this writer, whose