the great quantity of hydrogen gas extricated after putting in the alkali can only proceed from the decomposition of the moisture in the caustic potash, by means of iron.

This metal was first procured by professor Davy, in the progress of his most interesting experiments with the Galvanic battery. The method of procuring it by means of iron we owe, I believe, to Thenard and Gay Lusac. Our Dr. Woodhouse, before his death, certainly decomposed caustic potash by fusing it in a close crucible with lamp black, and procured a substance that took fire in the air. Curadau in 66 Ann. de Chimie 97, (36 Phil. Mag. 283) proposes the same kind of process without once noticing the experiment of Dr. Woodhouse.

The following are the different kinds of apparatus yet contrived for distilling pure potash over iron.

Fig. 1. The apparatus used at the Royal Institute. 25 Nich.

Jour. 191.

A common gun barrel, very clean inside, has an iron receptacle A ground into one end of it and furnished with a ground stopper, capable of holding 2 or 3 ounces of fused potash. Clean iron turnings are placed in the curve at D, and brought to a white heat. The potassium distils over at B, which is kept cool. Common air is excluded by a glass tube C, which supports a column of mercury. The tube is cut to get at the potassium.

Fig. 2. Mr. Johns's apparatus, by which the tube is saved, and the experiment may be repeated without destroying any part of the apparatus. 35 Phil. Mag. 321.

An iron gun barrel is cut in three pieces: the first, A a; the second forms the curve a L; the other is the strait piece or alonge G. This is fitted to L, by accurately grinding the one end to fit into the projection of the curved barrel. Mis a stop cock, I a glass tube, K a small basin containing olive oil. H is a tube of sheet iron, about six inches long, one half of which is inserted in the curved part L, and the other in the strait part of the barrel G, before they are fitted to each other. The potassium distils into this, and is more easily collected than if the barrels alone were used. The furnace is an eight inch black lead crucible, urged with a bellows. Of which the nozzle is shewn at F. B is the stopper to A, which is the receptacle of the pure potash.

A is kept cool till D is at

a white heat. G is kept cool during the whole operation, to condense the potassium. As soon as absorption appears in the end of the glass tube immersed in oil, turn the cock at M.

Fig. 3. The apparatus which I used, as fixed in a portable air furnace, nine and a quarter inches internal diameter in the widest part.

A, the furnace, with a hole in the upper part to feed the fire, and a hole below for the ash hole and draught. It consists of two parts, one placed on top of the other where the gun barrel appears outside. It stands on an iron tripod.

-B, the place where the strait tube is joined to the curved tube, by accurate grinding the one with the other, then fastening them with three small screws, and luting with fat lute to exclude all chance of moisture.

C, the thick or breeching end of the gun barrel, in which the caustic alkali is put, at twice.

D, the common screw of the breeching of the gun barrel; when all the alkali is in and begins to flow, fix the screw in a hand vice, and put it in its place.

E, the small brass cock, inserted in the strait iron tube by means of a cork, and, then luted with fat lute on a strip of linen and tied.

F, the place where the glass tube is inserted into the nose of the brass cock by means of a cork, perforated by a hot iron the size of the tube. Smear it before insertion with a little fat lute, and fix it tight with some tow.

G, a small basin, containing about half a pint or more of olive oil.

H, a brazed sheet iron tube inserted at B, half in one barrel and half in the other; 6 inches long. The strait tube may be kept cool by a damp cloth repeatedly employed between E and B. It may be supported by a piece of board underneath resting on the ground. Take care no water runs down to the cock or into the basin.

When the absorption begins in the glass tube, after all the hydrogen is expelled, turn the cock and prevent the oil from rising more than half way up the tube.

Upon the whole Johns's is the cheapest apparatus. The labour of bending and grinding and fitting the gun barrel, and the gun barrel itself, is lost each time in Mr. Davy's method, which in this country cannot be an expense each time of much less than one and a half dollar.

FOR THE PORT FOLIO.-AN ESSAY ON SCIENCE.

If the limited empire of man be capable of procuring happiness; if his contracted views of the surrounding greatness and splendid glory of Nature's fabric, be a sufficient source of real, uncontaminated felicity; and if it be possible that the assiduous exercise of his collected faculties shall open to his enjoyment the delectable fields of pleasure, he must enlist under the banners of Science, tread the smooth and the rough paths where Genius may direct him. No longer shall his mind yield to the pressure of the iron yoke of the errors of the day. Reason, from her temple invites him as a guest to Nature's feast, and the cordial hand of Science embraces him as her advocate.

See him emanating from the dark abodes of Ignorance, his contracted genius expanding with his emancipation; and behold it in the flights of Eccentricity, soaring aloft to Heaven. No barrier, but Creation's confines stops it; no unexplored field remains neglected: the mountain's treasures, and the valley's rich contents, all yield submissive to his scrutinizing eye. O sacred Science! thou, whose pleasing anticipations kindle in the bosom of thy votaries the noblest sentiments. Thou, whose various walks, decorated with the laurels of Victory, conduct us to the hidden beauties of Creation, we venerate thy foot-steps, we admire thee as the great fountain of unmixed felicity! With thee for our guide, no scene fails to be a source of pleasure. The most minute objects are investigated with the keenest discernment, and in these, rather than in the stupendous works of Nature, we behold the beaming lustre of creative Wisdom. Thus a single atom glows with splendour while mountains dwindle into insignifi

cancy.

The faculties of man enlightened by Science, like the strength of vision increased by the microscope, enable him to look with pleasure on objects which before disgusted or failed to delight. He can view Matter, as at first, an undivided whole; he can trace it through its variegated forms and its transmigrating round; can anticipate its future revolution and its eternal existence, and reflect with pleasure on the harmony of Nature, by which not an atom is lost, nor a particle added to the primitive capitol of Creation. He beholds the relation subsisting between himself and all surrounding objects, and recognizes the same matter in all.

Hence drew the moral sage, th' enlighten'd plan,
That man should ever be the friend of man;
Should eye with tenderness all living forms,
His brother emmets, and his sister worms.

Science is useful to man, not only because it dignifies the mind and fills it with exalted sentiments, but on account of its importance in all the affairs of life, whether we employ it for the good of others, or for our own benefit. Its effects on the mind gratify us by reflection and enamour us with felicitated -prospects of the sublimest nature. We recall the past hours, when the mind grovelled in ignorance and rambled in error. We feel the liveliest sensations of Pleasure, and the sweetest emotions of Enjoyment on reviewing our progress, however imperfect it may appear. But here the imagination stops not; admitted as it were to the door sill of Nature's temple, we are ready to suppose we have learn ed nothing; but stimulated by the pleasures arising from present attainments, we press forward, boldly advancing to the magnificent apartments of Creation, in which our fancy may rove, our ambition feast, and all our faculties flourish in the green pastures of Science. Where, where will you fix the bounds of man's imagination, when the torch of Reason illuminates his paths, when the polar star of Truth twinkles before him. Like the eagle in its flight, it traverses the Heavens, and like the Earth in its revolutions round the Sun, it soars and roves without control. Like a bird of prey, it seizes every object within its extended grasp, and furnishes the mind with a fund of felicity inexhaustible. How

sweet, how enticing are the smiles of Science, how decoying her allurements; how happy the man who is cntangled in her net! He beholds all things with a microscopic eye, and peruses with delight the fair, unsullied page of Nature. Her opened book is placed before him; from every leaf a world of wonders rises to excite his admiration and to gratify his ambition. His happiness enlarges with his advancement, and distant objects invite him to the consummation of his felicity. He smiles on Futurity, and anticipates all its prospects, confiding in the order of the operations of Nature. He beholds all events as certain and independent of Chance, since the same eternal laws that have regulated the Universe, still govern and control it.

"Through nature, he looks up to Nature's God." He seems, as it were, placed nearest on the list of effects to the Great Cause that has produced them. How different his situation, how widely different his enjoyments from those which result from Ignorance and Error! Are there, indeed, pleasures resulting from Ignorance? If there be any, their duration must be fleeting; their impressions as feeble. Educated in the vulgar opinions of the day, fettered with the trammels of heathenish superstition, man is little superior in the faculties of his mind to the beast that ran ges the forest. He beholds all the objects around him, yet literally sees nothing. He is necessarily concerned in the affairs of Nature; yet to all her operations he is a stranger, and they, to him, are but names of existence. Instead of forcing his way into the mysterious caverns of Creation, he stands neglectful and careless, and suffers mysteries to press upon him without the smallest anxiety or desire of investigating them.

Comets may blaze unseen, and worlds decay,

While Error leads, and man pursues its way.

But, to return to the pleasures of Science:-As the traveller who seeks repose beneath the umbrageous verdure of the oak, and whose heart gladdens on heholding a rivulet in which he may quench his thirst, so the enlightened man, fatigued with. the common pursuits of life, retreats in silence to his favourite study, and drinks of the cheering waters of the overflowing streams of Science. If his engagements be not accompanied