rigid to permit of farther detachment. This detached ring, collecting about a single centre, leaves our earth with a single satellite. Some of the planets, such as Jupiter and Saturn, have two or more satellites, while Mercury is presumed to be devoid of any.

. Prior to its annulous stage, the earth was a rotating sphere of incandescent liquid matter, incarcerated within a superlativelyheated atmosphere. This period may be designated as the Zonular Stage in the earth's evolution; for if we examine minutely it will be found that neither the liquid globe nor its surrounding atmosphere is of uniform characteristic throughout, owing to the fact that each is made up of different substances, various in character.

Continued refrigeration and chemical assimilation were synergistic agents in the production of this stage. Through the operation of the latter, the constituent elements of the earth and the atmosphere surrounding it, would form numerous and various combinations, the number and nature of which would depend upon the natural affinities of the elements and the relative proportions in which they were respectively present in the admixture of gases and vapors. Simultaneous with the reduction of temperature these newly-formed compounds would be disseized of the power to retain their former gaseous form, and through the influence of this liquifacient would be condensed into a molten-liquid sphere, with an atmosphere of such volatile compounds as could retain their gaseous form maugre the reduction of temperature.

Throughout the liquid sphere thus formed and its circumambient atmosphere alike, would occur an expatriation of that uniform density and diffusion which prevailed notably during the Chaotic Stage, and in a less marked degree during the Foci-forming Stage. This condition of attenuate diffusion was succeeded by that characteristic from which the third-the Zonular-stage derives its name, to wit: the arrangement of the dissimilar and newly-formed com pounds-in compliance with the law of gravity-more or less completely in strata or zones, according to their respective densities.

The layers of the stratified liquid sphere and its cinctured atmosphere may be tabulated-commencing at the centre of the earth and progressing upward-as follows:

I. Mineralogical Strata.

I. A central metallic nucleus of very great density, surrounded

by a zone consisting of combinations with sulphur, arsenic, etc., and the heavy metals;

2. A zone of molten rock, considerably lighter than the former, and in which silica, present in minimum proportions, existed in combinations with a large amount of the bases-lime, magnesium, oxide of iron, and alumina-with but comparatively little potash;

and

3. An extensive zone of molten rock of comparatively little density, consisting of silicates with an excess of silica combined with alumina and alkali, but containing very little of the other bases. II. Meteorological Strata.

4. Such compounds as are volatile at a very high degree of temperature only; e. g., the chlorides, and particularly the chloride of sodium-the chemist's name for common salt;

5. A great zone of carbonic acid gas;

6. A belt of nitrogen with an admixture of oxygen; and

7. In the form of vapor, all the water that now forms the seas and oceans, and saturates the earth and atmosphere.

The mineralogical stratographical arrangement of the molten sphere may very properly be considered as approximately stable, since it was one which was not destined to be broken up by complete refrigeration, accomplished by the radiation of heat and the heat-absorptive power of the atmosphere.

The meteorological stratographical arrangement, however, was quite different. Here the individuality and continuity of the strata were broken up, alike by the tendency of the heated vapors to diffuse themselves, and the actual congelation and precipitation towards the surface of the glowing globe of those gases and vapors situated in the colder regions of the intensely heated atmosphere.

When this sphere acquired an indubitable permanency of configuration, it may be said to have passed to the crusted-spherical stage in its Prozoic progress.

The earth and its furnace-like atmosphere surrounding it, owing to the refrigeration occasioned by the radiation of the heat into space, would gradually cool down. Under this persistent influence a thin crust or film would soon be formed over the surface of the molten sphere. The film thus formed, constantly receiving accretions from within, gradually interposed a greater and greater impediment to the radiation of heat from the interior of the slowly cooling mass, until the process of radiation was materially impeded.

Eventually the earth's crust was reduced in temperature below redheat, and our planet became the theatre of life.

With this reduction of the temperature of the earth's crust there would inevitably be a corresponding reduction in the temperature of the atmosphere. This reduction of the atmospheric temperature would be gradually increased by the impeding of the radiation of heat from the interior of the refrigerating sphere.

Consequent upon this reduction of the temperature of the atmosphere was the condensation and precipitation of some of those elements which had previously been held in suspension in the lower strata of said atmosphere; such, for example, as the chlorides, and particularly the chloride of sodium or common salt. From the amount of this mineral substance contained in the ocean and known deposits, David Forbes has estimated that the quantity of common salt alone must have been sufficient to form a crust over the entire surface of the globe some ten feet in thickness.

In speaking of the salt contained in sea water, Michelet says, that were it practicable to accumulate the entire amount upon the surface of America, it would form a mountain 4,500 feet in height, with a base co-extensive with the entire continent. And Reclus has estimated that, if the ocean were evaporated, for every fathom of water there would be an average deposit of two inches of crystallized salt. Assuming the average depth of the ocean to be three miles-which is not at all improbable-according to the above rule of computation, the ocean's complete evaporation would give us a salt-deposit over the entire basin of the ocean of about 230 feet in thickness.

Chloride of sodium, however, is not the solitary substance to which the sea owes it saltness, yet it is the principal one. And to this mineral are to be attributed the peculiar flavor and odor of sea-water. The quantity of common salt dissolved in sea-water is always 75.786-or a little more than three quarters of the total amount of mineral substance held in solution. The average quantity of salt contained in the sea-that is, the average degree of salinity of sea-water-has been estimated by Bibra and Bischof to be 35.27 parts in 1000. The more recent and more complete observations of Forchhammer, however, have shown the true proportion to be 34.4.

This saltness of ocean-water, however, is not a constant quantity, but is subject to innumerable variations, occasioned (1) by the

quantity of chloride of sodium dissolved; (2) the amount of evaporation and replenishment carried on in the particular region observed; (3) the amount of fresh water supplies furnished by rainfalls and river-discharges; (4) the direction of the currents and counter-currents-in short, every variation of temperature, every discharge of fresh-water, every local movement of the ocean, produces a more or less perceptible modification in the relative salinity. Systematic observations scientifically conducted have shown that the per cent. of saltness is invariably lower in the waters of the ocean in the southern hemisphere than in the northern. And in the northern hemisphere, where the ocean receives no supplies of fresh water from river-discharges, and very little from rain-falls, as in the North Atlantic, off the coasts of Morocco and the Great Sahara, and where the evaporation is very great, the saltness is nearly ninety-eight parts in one thousand. In mid-ocean, and particularly in the neighborhood of those shores where the waters of many large rivers are discharged into the ocean, the saltness is one, two, or three thousandths less.

In all mediterraneous basins, such as the Mediterranean Sea, the Caspian Sea, the Baltic Sea, and the Red Sea, the saltness of the waters is greater or less than in the ocean, according as the evaporation is greater than or inferior to the quantity of fresh-water accretions received from rain-falls and river-discharges.

The following table of comparative salinity may enable us to form some idea of the variability of oceanic saltness.

As already stated, chloride of sodium or common salt constitutes a little more than three quarters (75.786) of the total amount of

mineral substance held in solution in sea-water. This proportion of chloride of sodium to the other minerals, unlike the degree of salinity, is a constant quantity. This has been abundantly shown by the analyses made by various experimentists.

As refrigeration progressed, and the temperature of the atmosphere became reduced and the gathering and congelation of the gaseous particles was inaugurated, a scene of terrible sublimity was ushered in-such a scene as human eye never beheld, and one which earth was destined to witness but once. Wisps of cirrus swept along the unobstructed stammel concave; vivid and angular flames lit up with scarlet the Cimmerian gloom; while the deeptoned thunder ever and anon, in world-convulsing crescendoes, pealed forth its sublime and terrifying melody. The cirrus which at first did scarce stain ether, gradually deepened, and by swift degrees, spread a thick coat of distended nimbus over the canopied void of heaven. The clouds open and the vernal shower descends in one unbroken sheet; but, like the light of the rapid-shooting meteor that darts athwart the concave of" the inverted bowl," vanishes in mid-heaven and is returned to the upper regions, whence it proceeded. Again it approaches the earth's blackened and arid crust, and again it is scorched to evaporation and returned to the clouds which were already over-burdened with all the water that now fills the oceans and seas and lakes and rivers, and all that saturates the earth and rock and atmosphere. Eventually in the fierce conflict between the two elements-fire and water-the latter prevails, and the whole ocean is precipitously transferred to the parched crust of the famishing earth.

This seething ocean dissolved the encrustment of chloride of sodium, and with the cessation of its ebullitions it had acquired a salineous quality-which it has ever since retained.

The peculiar characteristic of color remains yet to be considered in endeavoring to account for the origin of the ocean.

The waters of the ocean possess the most vivid colors, the greatest delicacy of tints, and the most highly-graduated susceptibility found anywhere in nature. In the course of the seasons and the succession of day and night, are pictured upon its billowy bosom the sombre gloom betokening the imminent storm; the oppressive loneliness of gray twilight; the glory of "the advancing spars of day" as they quit the chambers of the orient; the gelid prospect of polar ice-locked landscapes, and the brilliancy of a tropical noon