And

1. THE next class of rocks are the clays that are found beneath every bed of coal, which are known as under-clays, or warrant, or spavins. They vary very much in mineral composition. Sometimes they are soft unctuous clay; sometimes clay mixed with a certain proportion of sand; and sometimes they contain such a large proportion of silicious matters that they become hard flinty rock, which many of you know under the name of "gannister." But all under-clays agree in two points. They are all unstratified; they differ totally from the shales and sandstones in this respect; and instead of splitting up readily into thin laminæ, they break up in irregularly shaped lumpy masses. they all contain a very peculiar vegetable fossil called "stigmaria,” which are branched vegetable fossils, dotted all over with little pits, and from these run out in every direction into the clay innumerable black filaments, sometimes to such a great extent that the whole clay is one thickly matted mass of them. This strange fossil was for a long time a sore puzzle to fossil botanists. At last Mr. Binney solved the problem by the discovery of a tree embedded in the coal measures, and standing erect just as it grew, with its roots spread out into the stratum on which it stood. These roots were stigmaria, and the stuff into which they penetrated was an under-clay. It is not very often that we still find the trees standing erect, because certain circumstances have generally thrown them down; but even when we do not find these trees standing erect, we often find them in very large numbers in the roof of the coal, having evidently been tossed over, and lying there flat and squeezed thin by the pressure of the measures that lie above them.

2. Lastly, we come to coal itself. How were these huge masses of vegetable matter brought together? and you must realize that they were very large masses indeed. Just to take one instance. The Yorkshire and Derbyshire coal field is somewhere about 700 to 800 square miles in area, and the Lancashire coal field about 200. Well, in both these coal fields you have a great number of beds of coal that spread over the whole of them with tolerable regularity and thickness, and very often with scarcely any break whatever. And this is only a very small portion of what must have been the original sheet of coal; so that you see we have to account for a mass of vegetable matter perfectly free, or nearly free from any admixture of sand, mud, or dirt, and laid down with tolerably uniform thickness over many hundred square miles. At one time it was supposed that the coal was formed out of dead trees and plants, which were swept down by rivers into the sea, just in the same way as shales and sandstones were formed out of mud and sand so swept down. It is not very easy to see how in this way such a light matter as dead wood could be spread with this wonderful regularity and uniformity over such very large areas. The fatal objection to this theory, however, is, that rivers would not bring down dead wood alone, but they would bring down, besides, sand, mud, and other matters, and that in the bottom of the sea the dead wood would be mixed with these matters, and instead of getting a perfectly unmixed, or very nearly unmixed, mass of vegetable matter, we should have a mixture of dead plants, sand, mud, and other things, which would give rise, certainly, to something like coal, but as any one who tries to burn such coal will soon find out, to something very different from a really good, pure house coal. So that this theory, which is generally known as the "drift" theory, was totally inadequate to account for the facts as we know them. The other theory was that the coal was formed out of plants and trees that grew on the spot where we now find the coal itself. On this supposition we could very readily account for the absence of any foreign admixtures of sand, mud, or clay in the coal; and we could also understand, very much better than by the aid of the drift theory, how the coal had accumulated with such wonderful regularity and uniformity of thickness over such very large This theory was for some time but poorly received; but after the discovery of Sir William Logan that every bed of coal had a bed of under-clay beneath, and the discovery of Mr. Binney, that these under-clays were true soils on which plants had

areas.

undoubtedly grown, there was no doubt whatever that this was the real and true explanation of the matter. I daresay that many of you have had occasion to walk across peat bogs, for there are many of them to be found within a few miles of Manchester; and it is not at all a hard thing to find, within a few hours of one another, a section of coal and its under-clay, and a section of peat bog made by one of those deep gullies which you find in all large peat bogs, and the resemblance between the two is very striking indeed. The peat bog is a great mass of vegetable matter, which is every year growing thicker and thicker; and underneath it there is almost always a bed of thin clay, in look very much like the under-clays; and this thin clay is penetrated by the rootlets of the moss forming the peat, exactly in the same way as the under-clays of the coal measures are penetrated by the stigmaria and its rootlets. But you must not suppose that the plants out of which coal were formed were exactly the same as the low type of moss which form our present peat bogs.

3. You will have noticed that there is one step more wanted to make complete this theory of the growth of coal on the spot where we now find it. The coal is found inter-bedded with shales and sandstones. These shales and sandstones we have seen were formed beneath the water of the sea, and as long as they remained there, of course no plants could grow upon them. The question is-how was a land surface formed for the growth of plants? It must have been formed in some way or other by the sea bottom having been raised above the level of the water. Now we have distinct proof in very many cases that elevation of the sea bottom and depression of the land is now going on in many parts of the earth's surface. And, therefore, we shall be assuming nothing beyond the range of our experience if we say that such elevations and depressions went on during coal measure times. The coal measure times must have been times during which the same spot was, now below the sea, and now dry land, over and over again. There was a land surface on which plants sprung up and grew fast, and multiplied rapidly, and as they died, fell and accumulated in a great heap of dead vegetable matter. After a time this layer for "layer" would be a better word than "heap"-of vegetable matter, was slowly and gently let down beneath the waters of the sea,-so slowly and gently that the water flowing over it did not, as a rule, disturb the loose pasty mass. And then, by the method I have described to you, shales and sandstones were deposited on the top of this mass of

dead vegetable matter. By their weight they compressed it, and by certain chemical changes, which I shall not have time to go into, even if they were satisfactorily understood, this mass of vegetable matter was converted into coal. After a time the shales and sandstones which had been piled up above this stuff which was to form coal for the future, were again elevated to form a land surface; upon this another forest sprung up, and by its decay produced another mass of vegetable matter fit to form coal. This again was let down below the water, more shales and sandstones were deposited on the top, and this process went on, over and over again, till the whole mass of our present coal measures was formed.

DAVID MACBETH MOIR, a surgeon at Musselburgh, Midlothian, tender poet, and a humourist of the truest and most genial kind. "Blackwood's Magazine." He was born in 1798, and died in 1851.

THERE is an unknown language spoken
By the loud winds that sweep the sky;
By the dark storm-clouds, thunder-broken,
And waves, on rocks, that dash and die;
By the lone star, whose beams wax pale,
The moonlight sleeping on the vale,

The mariner's sweet distant hymn,
The horizon that before us flies,
The crystal firmament that lies

In the smooth sea reflected dim.

was an elegant and He wrote chiefly in

'Tis breathed by the cool streams at morning,
The sunset on the mountain's shades,

The snow that daybreak is adorning,

And eve that on the turret fades;

The city's sounds that rise and sink,
The fair swan on the river's brink,

The quivering cypress' murmured sighs,
The ancient temple on the hill,

The solemn silence, deep and still,
Within the forest's mysteries.

Of Thee, O God! this voice is telling,
Thou who art truth, life, hope; and love;
On whom night calls from her dark dwelling,
To whom bright morning looks above;
Of Thee-proclaimed by every sound,
Whom nature's all-mysterious round
Declares, yet not defines Thy light;
Of Thee, the abyss and source, whence all
Our souls proceed, in which they fall,

Who hast but one name-Infinite.

All men on earth may hear and treasure
This voice, resounding from all time;
Each one according to his measure,
Interpreting its sense sublime.
But ah! the more our spirits weak
Within its holy depths would seek,

The more this vain world's pleasures cloy;
A weight too great for earthly mind,
O'erwhelms its powers, until we find
In solitude our only joy.

So when the feeble eyeball fixes
Its sight upon the glorious sun,
Whose gold emblazoned chariot mixes

With rosy clouds that towards it run;
The dazzled gaze all powerless sinks,
Blind with the radiance which it drinks,
And sees but gloomy specks float by;
And darkness indistinct o'ershade
Wood, meadow, hill, and pleasant glade,
And the clear bosom of the sky.

mystery, a secret won

der. inter'pret, to explain.

SPELL AND PRONOUNCE

resound'ing, echoing
back.
In'finite, without bounds,

sublime', lofty, grand, sol'itude, loneliness.