bring the sediment into the altered state in which we now find it.

STEPHEN. Well, then, gneiss is an aqueous-igneous rock?

PAPA. You can call it that if you like, but I don't see that it is an improvement. And here I may mention that I only want at present to give you some general ideas about the structure of the earth, and then, when you have those, you can begin to read for yourselves; but just now I am omitting a great many things that are of importance for the sake of giving you a rapid outline of geology.

STEPHEN. Well but, papa, you told me what the definition of geology was, but John wanted to know what was the use

of it.

PAPA. The practical value of geology is very great to many classes: for instance, a geologist, after he has surveyed any district, would be able to tell whether coal would be likely to be found in it or

not.

Now you can see how useful that would be, and what a deal of money it would save any one who had imagined that there was coal there, if the geologist came and told him there was none, for otherwise he might have sunk shafts, and erected engines and pumps, all for no purpose.

STEPHEN. Oh, yes, I see it would be of use that way.

PAPA. Yes, and in many other ways, too, but I have not time just now to show you how. Why did not Mary come to learn a little about geology?

STEPHEN. Oh, she said that she had read that geology tended to make people infidels.

PAPA. I wonder what book said so, for geology does not do any such thing, and I think I can convince Mary of it. I will bring her to the next lesson, however, when I have time to give you one.

WHAT IS PHOTOGRAPHY? PHOTOGRAPHS, or "light pictures," are formed by the action of light upon a chemically-prepared surface. Every one knows how light fades or changes the colour of almost everything submitted to its influence. Darkness, or the want of light entirely bleaches many substances. Many vegetable juices change colour on exposure to light, and it causes a soluion of nitrate of silver and some other chemicals to assume a dark or black colour. Leaves and lace were first copied on prepared paper, by merely laying them upon it, and thus preventing the light from acting upon the part covered by their leaves, &c. The picture formed by a lens in a camera obscura was next made permanent by the action of light on prepared surface. The various colours and shadows of the picture act in different degrees, so as to produce from the coloured image in the camera a delicately shaded picture on the prepared surface. Various processes are required to render the pictures thus produced permanent, or to secure them from the further action of the light when the picture is once formed. Were this not done, the continued action of the light would obliterate the picture and reduce it to a uniform black.

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Photographic pictures are now taken on three different materials-silver, paper, and glass. The pictures on silvered plates are what are called daguerreotypes. They are much used for portraits; but their expense, the labour of cleaning large plates, the inconvenience and danger of their preparation from the mercury which must be used, and the metallic glare of the pictures, render them ill adapted for landscapes, which are now scarcely ever taken in this style. For some years, too, there has been no improvement in daguerreotypes. We have portraits taken five years ago, which have never beensurpassed.

In the late exhibition of the Society of Arts, there were no daguerreotypes. The whole of the pictures were on paper or glass. The pictures on paper were by far the most numerous. They are all the result of a double process. The picture first taken is called a negative. The lights and shades are in it all reversed, be

cause the light darkens the prepared paper just in proportion to its intensity, so that the light parts of a landscape or building are dark in the picture, and the dark parts light. This picture being laid upon another sheet of prepared paper, and pressed closely to it by a sheet of glass, the light parts allow the light to pass through and darken the paper beneath, while the shaded parts keep off the light from the paper beneath, and it therefore remains white or of a lighter shade; and this process acts SO uniformly and regularly in all the varying lights and shadows, that a picture is produced just the reverse of the first one, the inost delicate lights and shadows being accurately represented, as in nature. This is called a positive picture, and all the pictures on paper in the exhibition have been obtained by a similar process. As the transparency of the negative picture is of importance to obtain a good positive, some operators wax the negative to render it so. This is called the "waxed paper process." Others prepare the paper with albumen or white of egg. The most recent improvement is, however, the use of glass for the negative pictures. The glass is prepared either with albumen (white of egg) or with collodion, which is made of gun-cotton, dissolved in ether. This coating on the glass receives the chemicals to be acted upon by light. In the negatives taken on glass, the shadows are transparent, while the lights are opaque. The positive is then taken in the same manner as from a paper negative. The negative picture taken on glass by collodion may, however, be made a positive itself; for the lights which are opaque are rendered so by a light-coloured coating or film. By laying the glass, therefore, on some dark substance, the transparent parts become dark, and the opaque parts light, and thus a direct or positive, and often very beautiful picture is obtained.

If we wish to ascertain the advantages or merits of the peculiar styles, we must know something of the process, and consider which is most capable of further improvement, and of supplying those imperfections which at present exist in the art. For pictures of a limited size and of a neutral tint we can scarcely

imagine anything more perfect than the views exhibited by Mr. Owen, Mr. Buckle, and M. Constant, and the portraits of Mr. Sims. In the further progress of the art increased size, life, and colour, are the only desiderata. Of the production of colours, as in nature, there seems at present no sign in one process more than in the other. With regard to increased size, though the largest pictures in the exhibition were from paper negatives, we think that any one acquainted with all the processes would find it more difficult to manipulate a very large sized picture with paper than with glass. There seems, in fact, scarcely any limit to the size of pictures on glass.

The next point, that of obtaining more life in the pictures, must have struck every one. How much would sheep and cattle add to the beauty of many of the landscapes, and figures to the architectural views; while in the eastern scenes we miss the natives in their characteristic costume to give life and reality to the whole. In this, the collodion process is infinitely superior to the paper, the former not taking more seconds than the latter does minutes; and as the pictures can be in every other respect obtained equally good, this alone must decide the question of its being the process which offers the greatest facilities for bringing the art to a yet higher state of perfection.

In this view, the positive collodion process is superior even to the negative, and by it will probably be obtained the greatest triumphs in the delineation of living animal forms, and in catching the varying attitudes and expressions of the human figure.

Photographers owe to the Society of Arts the knowledge of what has been done and is doing, both at home and on the continent; and when the next exhibition takes place, we shall be able to judge what progress has been made in the direction in which we are now seen to be most deficient. This is one of the discoveries of Science, which will undoubtedly be subject to great and important changes, and we shall from time to time, whenever any decided improvements are effected, present the same to the notice of our readers, who are, no doubt, much interested in the subject.

THE DREAM OF LOVE.

HARTLEY COLERIDGE.

IT must be so-my infant love must find
In my own heart a cradle and a grave;
Like a rich jewel hid beneath the wave,-
Or rebel spirit bound within the rind

Of some old wreath'd oak, or fast enshrined
In the cold durance of an echoing cave.
Yet better thus than cold disdain to brave;
Or worse, to taint the quiet of that mind
That decks its temple with unearthly grace.
Together must we dwell, my dream and I.
Unknown then live, and unlamented die,
Rather than dim the lustre of that face,
Or drive the laughing dimple from its place,
Or heave that white breast with a painful sigh.

Light breezes will ruffle the flowers sometimes,-
The short, passing anger but seem'd to awaken
New beauty, like flowers that are sweetest when
shaken.

If tenderness touch'd her, the dark of her eye
At once took a darker, a heavenlier dye,
From the depth of whose shadow, like holy
revealings

From innermost shrines, came the light of her feelings!

Then her mirth-oh! 'twas sportive as ever took wing

From the heart with a burst, like the wild bird in spring;

Illumed by a wit that would fascinate sages,
Yet playful as Peris just loosed from their cages.
While her laugh, full of life, without any con-
trol

But the sweet one of gracefulness, rang from her soul;

And where it most sparkled no glance could discover,

In lip, cheek or eyes, for she brighten'd all

A STARLIGHT WINTER NIGHT.
THE stars are forth, the moon above the tops
Of the snow-shining mountains.-Beautiful !
I linger yet with Nature, for the night
Hath been to me a more familiar face
Than that of man; and in her starry shade
Of dim and solitary loveliness,

I learn'd the language of another world.
I do remember me, that in my youth,
When I was wandering, upon such a night
I stood within the Coliseum's wall,
Midst the chief relics of almighty Rome:
The trees which grew along the broken arches
Waved dark in the blue midnight, and the stars
Shone through the rents of ruin; from afar
The watchdog bay'd beyond the Tiber; and
More near from out the Cæsar's palace came
The owl's long cry, and, interruptedly,
Of distant sentinels the fitful song
Began and died upon the gentle wind.
Some cypresses beyond the time-worn breach
Appear'd to skirt the horizon, yet they stood
Within a bow-shot.-Where the Caesars dwelt,
And dwell the tuneless birds of night, amidst
A grove which springs through level battle-

ments,

And twines its roots with the imperial hearths,
Ivy usurps the laurel's place of growth;-
But the gladiator's bloody circus stands,
While Caesar's chambers and the Augustan halls,
A noble wreck in ruinous perfection!
Grovel on earth in indistinct decay.
And thou didst shine, thou rolling moon, upon
All this, and cast a wide and tender light,
Which soften'd down the hoar austerity
Of rugged desolation, and filled up,
As 'twere anew, the gaps of centuries,
Leaving that beautiful which still was so,
And making that which was not, till the place
Became religion, and the heart ran o'er
With silent worship.
BYRON.

BLIND MARY.

THERE flows from her spirit such love and delight,

That the face of Blind Mary is radiant with light,

As the gleam from a homestead through darkness will show,

Or the moon glimmer soft through the fastfalling snow.

Yet there's a keen sorrow comes o'er her at times,

As an Indian might feel in our northerly climes; And she talks of the sunset, like parting of friends,

And the starlight, as love, that nor changes nor ends.

Ah! grieve not, sweet maiden, for star, or for sun, For the mountains that tower, or the rivers that

run

For beauty and grandeur, and glory, and light,
Are seen by the spirit and not by the sight.
In vain for the thoughtless are sunburst and
shade;

In vain for the heartless flowers blossom and fade; While the darkness, that seems your sweet being to bound,

Is one of the guardians an Eden around!

WONDERS OF ART.

THE SUBMARINE TELEGRAPH.

Ir all the myths of the old poets were realised to-morrow, not one of them would stand a chance with the hard practical realities of the electric telegraph. The boldest story-teller of Rome or Greece never dreamt of annihilating time and space, even for the express purpose of making two lovers happy; and the most extravagant metamorphose ever imagined by Ovid might have been readily believed a century ago by the sternest philosopher of the age, if he could first have been

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to

made to swallow and accredit the prophecy that his descendants could walk down to Cornhill and receive a reply to message to Paris in a minute. The celebrated Hibernian bird which contrived to exist in the flesh in two places at once, must have encountered difficulties which the magnetic current is a stranger; and, except that ornithological phenomenon, of which no specimens at present exist, there is certainly in art or in nature nothing more wonderful than this mastery, which man, by the aid of a few plates of metal, some acid and wire, has obtained over the subtle fluid, the effects of which

are as patent and striking as its source is mysterious. The electric flash, the type of all that is swift and destructive in the elements, is here chained to the car of commerce, or wielded by curiosity or caprice. The message flies "ere one can say it lightens.' The electric fire is bottled up in little wooden cases with brass knockers and screws, or is served out at will from oblong jars under the counter, moulding itself into the inflections of every language, and adapting itself to the exigencies of every thought, and beating that old, but remarkably fast person, Old Time, hollow, whenever the race is long enough. There are some dissatisfied people who wish they had been born a little later; they want to see the full development, they say, of the twin giants, steam and clectricity; to listen to the first announcement of the great discoverer who shall pierce the darkness that hangs over the birth-place of those family connections whose exact relationship they as yet know not, and proclaim the parentage of Light and Heat, and lightning in its varied forms. It is privilege enough for us to live in an age when, science having ceased to be empirical and impious, devotes itself to the practical wants of man, and, astonished at its success, confesses still how little it knows of its future, without our grudging to those who may come after, the fruits of its more matured enterprise and experi

ment.

The project of constructing a submarine telegraph between England and France, across the Strait of Dover, unsuccessfully attempted in 1850, was again undertaken, and at length accomplished. The line or cable at present in use is much more substantial than that formerly employed, and was constructed in the following manner :-Four copper wires, known as the 16 wire gauge, each encased in a covering of gutta-percha, of a quarter of an inch in diameter, constituted the first layer. These several lines áre twisted and plaited about each other, in spiral convolutions, in the manner of an ordinary cable or rope. The next superincumbent coil to this consisted of hempen yarn, previously saturated in a reservoir of prepared pitch and tallow, and, in its

impermeably and by steam power, over the gutta-percha, with its enclosed copper wires. This is overlaid again with a series of hempen yarns, five or six in number, and about an inch in diameter, saturated in the pitch and tallow, with a view of what the workmen call " worming" the gutta percha. The gutta percha thus protects the wire, and the hempen yarn in addition acts as a cementitious material to the gutta percha, which, ultimately, has thrown over it a coat of galvanized wire. This completes the first process, and the manufacture of the rope in the spiral form is for the purpose of giving flexibility. The second process consists in hauling off the cable, so far completed, and passing it on to another wire-rope machine, where the cord is completely covered over with ten galvanized iron wires, each wire being about the thickness of a lead pencil, and known as "No. 1 galvanized wire gauge." This galvanized iron sheathing is to protect and preserve the interior layers from the action of the sea, and the weight is considered to be sufficient to sink the cable ex necessitate gravitatis. The accompanying engraving will explain to the reader this curious pro

cess. A, the four conducting copper wires. B, covering of gutta percha. The double covering of guttapercha is more clearly explained by the section C, spun yarn, saturated with tar, wound round the covered wires, and filling up the in

E.

terstices so as to form a core upon which the galvanized wires are laid. D, outer

protection, consisting of ten galvanized iron wires. E, section