little stream, which froze on the slightest provocation. So the first notion was to make the Arc "run" its own water uphill. This was found too costly; and soon a simple machine was invented, so effectual withal that it has now superseded the Brunelesque water-column even on the Piedmont side. Imagine an inverted siphon with equal legs, like a great flat-bottomed U. Horizontally along the flat base moves a piston, worked by a waterwheel outside (which, of course, needs only a fall of a few feet.) Half up each leg the siphon is filled with water, and the legs are closed at the foot. Of course when the piston moves one way it forces the water up and compresses the air in one leg, leaving a void in the other leg, which is at once filled with the outer air, let in through a valve. The next stroke reverses the motion of the piston, and compresses the air in the other leg. As the air gets compressed it is forced through another valve into a cast-iron chamber, where it is kept for use. By this process it is found that air can be readily compressed to one-sixth of its volume; and though the force is far feebler than that of the hydraulic pressure, it is just as effective, because the motion is so much more rapid. Of course there are a great many of these siphons at work; indeed, the air-compressing works give one the notion of a grove of iron coral-such coral as we may suppose grows in the moon, or wherever our meteorites come from. There are great metal pipes branching and twisting in all sorts of ways; and from the grove an iron snake, sometimes above ground, sometimes buried (to avoid mishaps from landslips,) pushes on into the tunnel. Then, to keep up the metaphor (which is not ours, good reader-we are not half poetical enough for such a flight of fancy; it is due to M. Munos, whose able paper in the Revue des deux Mondes for February 15th details in full what we are only giving in brief summary,) our snake (buried during that parenthesis) shows a strange, uncomfortable-looking head, from the jaws of which dart out, quick as lightning, some score of iron tongues, while at each dart comes out a puff, not of the traditional deadly serpent's breath, but of good fresh air, at high-pressure, strong enough to keep up an excellent ventila

tion.

Herein lies the great value of the machine, as contrasted with the steamengine of which we spoke above; the air at the head of the works is far fresher and purer than it is nearer the mouth. In one or two points theory is found, as far as this machine goes, contradicted by practice. A law of mechanics is, that power can never be multiplied without generating heat. All the croakers, said to Deputy Sommeiller (for he was sent up to the Turin Parliament till the priests, naturally mistrusting a work which the Encyclical would be sure to condemn, turned him out,) "All your tools will get white hot; all your pipes, too,-solder will never hold at the joints." But, strangely enough, the temperature is scarcely raised at all; and though the wear and tear of chisels is enormous, it is solely due to the hardness of the "metamorphic" rock; the "machinery," in contact only with water, never gets worn at all. They rather dread the time when they will get to the still harder " 'quartzite," which forms the centre of the mountain mass : even now a hundred and fifty chisels are blunted for every yard or so of work.* The other strange fact is, that there is scarcely any appreciable loss of power in transmitting the compressed air through the tunnel. Steam condenses rapidly; but compressed air is found very nearly as good as ever, twenty-four hours after it was made, at a mile and a half from the "generator," The only danger is the bursting of the chambers or conveying pipes. They had several discouraging accidents at first; but now it all seems well under hand; and the number of siphons and chambers stopped off from one another, makes anything like a general blow up impossible.

Now of course our iron snake is not all in one piece. How do they join the pieces of piping together? The rough and ready way which answers with gas-pipes won't do. Even there, as your nose will tell you if ever you pass along a street when the pavement is up, there is a constant discharge-enough to lessen the dinamical effect. Besides, the gas-pipes are snug and warm under ground: this

Since this was written, we see that the centre of the mountain has been reached, and is found to consist not of quartzite, but of soft calcareous deposit; so the work goes on merrily.

air-tube is mostly on the surface, in a climate of great extremes. Every child knows how readily iron expands and contracts. A severe frost might leave an awkward gap in the best constructed iron joint; so the lengths of cast-steel tubing are put together with an "expansion joint," craftily constructed of overlapping lips of strong india-rubber, with an india-rubber jacket over them, and an extra stout canvas wrapping over that. One lip is wider than the other, so that one tube can slide a little way over the next, "like the rings in an elephant's trunk." The work is so perfect that you may pass a light along the whole length, when the air is at high pressure, without making it even flicker.

And now we must walk into the tunnel: it is full eight yards wide, is lighted with gas, and has all along a tunnel a yard deep, to carry off the drainage, and to shelter the men in case any of the rock should give way. As we go along we see at the sides an army of men enlarging by the usual means the little passage (about eight square yards-a very different thing, Miss or Madam, from eight yards square) made by the machine. There they are, perched up on scaffoldings in all sorts of unexpected places; and every now and then, when a man has "picked" out a load, he draws a bolt, and down through a trap tumble the blocks into a wagon below, and get wheeled off along a tramway. But there, where the tunnel grows suddenly narrow, stands "the machine." With its array of chisels and pistons it looks like some strange war chariot. But, hark! that is the signal for the workmen to "take care;" and up rushes a sort of tender, pushes this machine close up to its work-and then, with a fearful puff, out come the pistons, in dash the chisels, with a scraping and grinding indescribable; and, hurrah! we have pierced as much deeper into the Alps as twenty stout workmen could have done. Puff and stroke number one are followed up by puff and stroke number two; and so on for six hours; in which time they make some hundred holes, about a yard deep and from one to three inches across. Then the air-machine has a rest; the holes are plugged with powder, and exploded in the usual way, the workmen

sheltering behind the tender. The moment the blasting is over, all the strength of the compressed air is turned on to clear the tunnel from sulphurous and carbonic acid. It clears the far end most effectually; but now that the work is getting on, the vapors lodge about the middle, and have to be pumped out.

Owing to the number of holes, the rock is broken up into quite small blocks, so that three hours is enough to clear away the rubbish; hence they manage to get three piercings in the twenty-four hours. The machine" keeps along what is to be the floor of the tunnel; and, as soon as it has passed, workmen begiu widening and heightening. But how if the works begun at the two ends should not meet in the middle? There would be a pretty fix. Just try in the first big cheese you get hold of, and you will find it not the easiest thing in the world to make two skewers meet across its breadth. How can these miners be certain of their work? Here trigonometry steps in to make that a matter of certainty which, without it, would be doubly working in the dark. Ah, master schoolboy, you find your Euclid dull, do you? You talk nonsense about the asses' bridge,—so called, remember, on account of those who can not get over it. Let me tell you, that but for that same dull Euclid we should have no surveying, no decent railways, no maps, except such as any black fellow could trace in the sand for Captain Speke or Dr. Livingstone. The first thing was to survey a straight line right over the mountain between the two ends. This was hard work, up a veritable goats' track; but it was done at last; some of the angles being taken sixty times over with the grand theodolite of the French railway engineers' staff. It took a long time: often, just as everything was ready for an observation, a mist came on and hid the "object" for hours, perhaps for days. However, it was well done; and the line of tunnelling being thus fixed once for all, it is easy to keep it true by having a light at the far end, and “observing" it every now and then from the marked positions outside. The level, too, has to be kept, or one half might overshoot the other, for both rise slightly from the outside. Among the minor difficulties was the feeding of the work

men, two hundred at each end, in a hungry land where nothing indigenous was to be had except a few chamois. All the machinery, too, was made in Belgium, at Seraing, and it was very hard to get it to the Piedmontese side; indeed, all their roads had to be remade before it could be carried to Bardonnesche.

And now how long has all this been going on? The work on the Italian side began in good earnest early in January, 1861; that at the Savoy end two years later. A beginning had been made on each side by hand, the works being so long in getting into gear. At first they did very little, working with only one perforator, and then with three or four; now, as we said, a fair day's work gives three yards on each side. The total length will be some eight miles; and in six years more it is calculated that the two colossal graving tools will meet, and the passage to Italy be ready for

use.

What a happy thing it is that the supply of air is inexhaustible! The quantity required increases at an enormous rate; for every new gas-light consumes so much more oxygen, and every blasting throws out fresh deleterious matter to be counteracted; so that it is sometimes a question whether the grove of siphons will not have to become a forest.

Yet nev

When we think of the extreme simpleness of the means employed, the result is perfectly marvelous. We are accustomed to the wonders of the hydraulic press; and so M. Sommeiller's former plan, which brought a column of water from a height of fifty yards to bear on the surface of air, seemed straightforward enough; but these siphons with the piston inside-it seems too easy. ertheless it works; ça marche, say the French, for, with our Gallic neighbors," water never does anything more inanimate than walking. But we are forgetting one main point. A tool worked by hand has three motions impressed on it; it makes the blow, it rotates, and it moves forward. The pistons manage the first, furiously discharging their chisels against the wall of rock. The rotation is most ingeniously managed; the base of the tool is cogged, and by means of a cog-wheel and ratchet-itself the

piston of a very small subsidiary aircylinder-it contrives that the chisel moves round one tooth at every stroke. The advance is provided for by a spring, which is released, when needed, by the opening of a valve, and forced back, when it has done its work, by the rush of the air.

"May I be there to see," is what one naturally says when one looks forward to this time six years. What rejoicings there will be in "plucky little Piedmont," which found the courage to begin, and most of the cash to keep it going! what wild delight in Savoy, which found the "inventor;" which actually sent up to Parliament the man who, then and there, made a speech about his tunnel, and got patted on the back by Menabrea and Palescafa, and taken by the hand by Cavour! what "felicitations" from the French, whose Ponts et Chaussées, apparently a very red-tape office indeed, pronounced it as wild a scheme as squaring the circle! France would very probably have let it drop had not Piedmont made the carrying out of the plan a special clause in the treaty by which Savoy was ceded.

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When Cavour took a man by the hand he seldom dropped him. This makes us independent of England and her coals," said he. Possibly he believed in the "grand future" which some people hold to be reserved for "compressed air;" and looked to see it laid on," like the water or gas, all through manufacturing towns, a blessed, smokeless, heatless "motive power." Doubtless he took up M. Sommeiller all the more strongly because the priests, who care not a jot for Alp-piercing or anything else, in comparison with due subservience to "mother Church," tried to keep him down. And so, in 1856, the "tunnel bill" passed the Turin Parliament (alas, for that good little Parliament!may they make as good a hand of things at Florence or Rome), and commissioners were appointed to "report," who, by the way, went to work so lazily that Cavour took them to task in pretty severe style.

Poor man, to him we owe both Italian unity and the tunnel that is to unite Italy with the rest of Europe. He lived to see neither; but he certainly gave the

impulse to both. This day six years, let us hope that both will be "accomplished facts:" that Rome and Venice will be very different from what they are now; and that, under the old highway by the Cottian Alp, the fire-carriage will pass and the electric message flash, "annihilating," as the newspapers say, not only space and time, but also the mighty barrier of the everlasting hills.

It is a grand thought that so simple a principle, the principle of the intermittent spring, observed ages ago by Hero of Alexandria, and used by him in his high-pressure fountain, should be found effective in such a gigantic work-that the air-wrought tunnel is well on in corso de scavazione.

One consolation we may glean from M. Sommeiller's success: when our coal shows signs of failing (as the Spectator lately told us it will in a few hundred years), we need not shut up our workshops for want of "motive power." All we shall need will be a little more patience than we have hitherto shown in working the "atmospheric."

Fortnightly Revi w.

THORVALDSEN AND HIS ENGLISH CRITICS.

THERE is something very charming in the respect which the Danes pay to their literary and artistic heroes. Oehlenschläger has his monument in the most public square of Copenhagen, his eyes of stone look quietly on every traveler who passes up from the quay to the Hotel d'Angleterre; Thorvaldsen has his museum on a site immediately adjoining the royal palace; and when Hans Christian Andersen, immortal in nurseryland as the author of the "Ugly Duckling," walks through the capital, gentle and simple take off their hats to him. A successful Danish writer or artist, resident in Copenhagen, occupies much the same position as the local luminary of an English town or the accepted genius of a Scottish weaving village. He is a big man there, though he might be a very little one if he ventured out into the great world. We would not suggest, indeed, that, to use the Baconian phrase, he is a figure among

ciphers; but it is certain that he is not measuring himself with giants. Danish art is barren enough. Danish literature is not very strong; since, from the period of the national ballads downwards, it has contented itself, perhaps wisely, with a narrow range of thought and feeling. The marked notabilities might be counted on one's fingers. Oehlenschläger, with his strong Scandinavian vigor, struck some powerful notes out of the national harp, and was, in a limited way, a man of dramatic instincts; and young Björnsterne Björnsen (who is, however, at least half a Norwegian) possesses a fine poetic vein, sombered with Lutheran piety. But in our opinion, the national power culminated in Thorvaldsen, who, besides being a fine sculptor, was a thoroughly representative man. He was a genuine Dane, warmhearted, excitable, obstinate, courageous, yet with an undercurrent of luxurious laziness; worked best when his blood was up, and worst when he was thoroughly comfortable; had a kind of sea-salt in his composition, which naturally gave his conceptions a tinge of that vigor which is apt to thicken into coarseness. He was

a great artist with all a great artist's littlenesses a thorough-going specimen of the genus irritabile. His countrymen, conscious of his greatness, have done him those honors in which, more than most people, they delight; his Museum is one of the sights of the world, and loving hands daily strew flowers on the tomb which lies in the centre thereof. That, as a sculptor, he has been overrated by many, we are not disposed to deny; it is a fact very vehemently insisted upon by a small section of the art-public-that exquisitely fastidious section which places so much stress upon mere technicalities. His work abounds in faults; what more natural, seeing the man's education was so imperfect? Had he known a score of languages, and penetrated deep into many mines of learning, he would never have worked off the roughness contracted in a Copenhagen hovel and ship-yard. Nevertheless, he did much for the world; his "Christ and the Apostles " alone forming an important point in the history of sacred art. But of what he has done for that little nation from which he sprung we feel it difficult to make too high an estimate. He represents in art the cour

age, the energy, and Christian sincerity, as well as the narrow-mindedness, of his countrymen ; and has gone as high as any Dane could go, still preserving all the precious traits of nationality. Shut out from the rest of Europe, so to speak, and fettered by the exigencies of a barren soil and a scattered population, the Danes can not hope to furnish, and do not wish to furnish, cosmopolitan contributions to art and literature; they must be local and individual, or nothing. Thorvaldsen, then, suggests all this. It was with no mere feeling of friendship that Oehlenschläger, in stirring and complimentary verse, welcomed him back to fatherland, and con tinued to sing of him while there; and it is with a sentiment of patriotism rather than of hero-worship that the Danes strew flowers over the grave in the Thorvaldsen Museum.

It is no part of our present task to attempt an examination of Thorvaldsen's contributions to Art, though we agree neither with those who would raise him to the hierarchies, nor with others who, like the friends of Canova, would hurl him to the region of the groundlings. A far more difficult question has been raised, one reflecting darkly enough on the sculptor's conduct as a man; and we have no hesitation in affirming that it has been raised by persons indelicate enough to carry the vehemence of artistic predilection into a discussion concerning moral right and wrong. The statue of Lord Byron may be very bad, but is that any reason for telling everybody that the sculptor had a very bad temper? The drapery of the "Christ may not lap quite perfectly in one or two places, but why fly from that statement to the assertion that the sculptor's morals were, to use a very mild word, uneven? The art-critic has one taste, the biographer another; and it is a pity that the one should so often appropriate the other's material. The enemies of Thorvaldsen discuss him something in the style of a person familiarly chatting in loose conversation. "You like Thorvaldsen, and he was undoubtedly a very clever fellow, but as an artist, bah! His Night,' I confess, is a pretty sort of thing, and there is a good deal of bold stuff in his Jason,' but he is shamefully overrated. You've heard of course what a brute he was to his father,

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and how shamefully he broke his engagements." This is bad enough to tell very well with the profane vulgar; but of course the tone is one intolerable to cultivated people. It is a tone familiar to lady novelists, who have, by the way, carried much of the "goody goody" feeling into biography, and in whose eyes a hero must be perfect. Obediently to the spirit which exaggerates trifles, we have whole scores of biographies crammed with good principles but destitute of a gleam of human nature; for it is a fatal mistake to imagine that, to understand a man, we must examine him in bits. Instead of finding out pretty actions or hunting for flaws, a true biographer takes a man as a whole, nor separates him from the background of the events and personages among which he lived and moved. Goethe did and said a great many small things, and has suffered to some extent from pigmy biographers; but we know well enough by this time that Goethe was a great man-albeit by no means (and thank heaven for that!) a "John Halifax." In biography, as in many other departments of art, we want a little more power of considering affairs dramatically. To get at a man's character rightly, we must put ourselves into the movement of his life; and when once we do this, we shall soon feel whether he be great, or mediocre, or small. Mr. Carlyle has his faults, but want of dramatic force is not one of them; and his short biographies, taken in the mass, are perhaps the best we possess. His manner of working is right, if his conclusions frequently be wrong; for while he never loses sight of his leading character, he takes care that all the minor parts are well supported. He carries us into the heart of a man's actual life, and if he has not previously converted us to hero-worship, we are at liberty to form our own impressions.

The son of a Copenhagen woodcarver and a Jutland peasant girl, Thorvaldsen very early began a struggle out of which only a strong man could come victorious, and in the course of which the very strength of a man would be sure to breed numberless weaknesses. His parents resided in a poor house in the immediate neighborhood of the docks, the occupation of Gotskalk, his father, being to carve wooden decorations for the vessels.