Слике страница
PDF
ePub

LITERARY AND SCIENTIFIC INSTITUTIONS.

one or both of the metals become oxidated, or corroded. The conductors of electricity are also conductors of galvanism: these are divided into two classes; the dry, such as metallic substances and charcoal; and the wet, as water and certain other fluids. The galvanic influence cannot be powerfully excited without a combination of three conductors, two of one class and one of another. When two of the three bodies are of the first class, (as two metals zinc and silver, or zinc and copper with water or an acid,) the combination is said to be of the first order. But it is an indispensable requisite, that one of the three conductors should have a chemical action on one or both of the others: thus water, as containing oxygen, has an action on the metals; if it is impregnated with oxygen gas its action is increased, and much more powerful than that of water deprived of air by boiling; and if a small quantity of any of the mineral acids is added the effect will be still greater. Thus the agitation or excitement occasioned by the action of an acid principle is important in the phenomena of galvanism, as the excitement occasioned by friction is in electricity.

It was then stated that some of the earliest galvanic experiments were made with an apparatus called by its inventor the couronne de] tasses, and it consisted of a series of wine glasses containing dilute acid, in which was immersed a series of zinc and silver plates; the gal vanic pile, however, soon superseded that mode of combining plates. In the pile the plates are placed upon each other in a perpendicular direction, pieces of moistened flannel being interposed between each alternate plate.

The power of an apparatus thus constructed gradually diminishes, the zinc surfaces becoming oxidated by the action of the fluid; and this is more particularly the case when acids are employed; it therefore requires to be taken to pieces and cleaned, an operation that is very troublesome where the number of plates is considerable. To obviate or rather to Jessen this inconvenience, subsequent experimentalists soldered each of the pairs of zinc and copper plates together, and a further improvement was suggested by Mr. Cruickshanks, which consisted in cementing the pairs of plates in regular order, in grooves made in the sides of mahogany troughs, so as to form water-tight cells between each pair. These cells being filled with water, or any conducting fluid, served as a substitute for the moist ened flannel used in the pile; and as the fluid could be easily poured out, and re

363

[merged small][ocr errors][merged small]

that metal in an iron or brass mould; they The zinc plates are made by casting

may be about an eighth of an inch thick. The copper need not exceed twelve or fourteen ounces to the square foot, and may be soldered to the zinc at one edge only, the other three being secured by cement in the trough. The trough must have as many grooves in its sides as the number of plates it is intended to contain, which should be the apparatus will be inconvenient from its fewer in proportion to their size, otherwise weight. When the plates are not more than three inches square, their number in one trough may be fifty, and the distance of the grooves from three-eighths to half an inch. The trough must be made of very dry wood, and put together with white-lead or cement. The plates being placed to the fire, the trough is to be well warmed, and placed horizontally on a level table, with its bottom downwards; very hot cement is then to be poured into it, until the bottom is covered this process the plates will have become to the depth of a quarter of an inch. During warm, and they are then to be quickly slided into the grooves, and pushed firmly to the bottom, so as to bed themselves securely in the cement. In this way the plates are very perfectly cemented at the bottom, and when this cement is sufficiently cool, a slip of thin deal is to be slightly nailed on the top edge of one of the sides of the trough, so as to overhang the inner surface about a quarter of an inch. The trough being about three quarters of an inch deeper than the diameter tween their top edges and the deal slip; of the plates, there will be an interval be and when the side of the trough to which the slip is attached is laid flat upon the table, this interval forms a channel, into it will flow between each pair of plates, so which very hot cement is to be poured, and as to cement one side of all the cells perfectly. As soon as the channel is quite full of fluid cement, the strip of deal is to be torn off, and the trough inclined, so as to ad. mit the superfluous cement to run out. When this is effected, and the cement cool, a slip of deal is to be nailed on the opposite that. The instrument will then be cemented side, and the same process pursued with in the most perfect manner, and it may be cleaned off and varnished.

described, the order of the plates is similar, It is obvious, that in all the arrangements the copper and zinc alternating regularly with each other; hence, if the first plate in any battery be zinc, the last will be copper; and in all cases the uncombined surfaces of the copper and the zinc plates are opposite to each other. That end of the battery to which all the copper surfaces are turned, is the zinc surfaces incline is called the zinc called the copper extremity; that to which extremity. When many plates are required, the power of several batteries may be combined together by connecting them in proper order, endways, with slips of copper: the usual rule is to connect the zinc end of one battery with the copper end of another, and so on; for in this way their plates tend all in one direction; if one battery, or even a few plates in an extensive series, should be reversed, a very considerable diminution of power will be šustaîned. ^

apparatus, consists in giving greater facility to its construction. This is accomplished by the use of Wedgwood-ware.or porcelain troughs, formed in the manufacture with compartments about half an inch broad, but about the same depth and length as the plates of ordinary troughs. Single plates of zinc and copper are united by a metallic arch at the top, so that they are parallel to each other, and at such a distance that the two plates can be placed in two adjoining compartments. When the battery is completed, each compartment is filled with fluid, and contains a plate of copper and a plate of zinc. This apparatus in fact combines the principle of the battery with glasses and that of the common trough. It has, from its convenience, been much used at the London Institution. As both surfaces of the metals are exposed to the action of the fluid, plates of the same size as those of the common trough expose twice the surface to oxidation; the galvanic effect is not, however, duplicated, although rather greater than with a single surface. The principal advantage consists in the facility with which the battery can be constructed, and the plates cleaned after having been used; it also admits of another adjustment, which is occasionally convenient; the plates are sometimes all united by a bar along the top of them; and they may then be raised or lowered by rack-work at pleasure, so that the charge can be reduced in any required proportion, and again increased to its full quantity.

the

If water be interposed between the wires from a voltaic battery, oxygen separates at the positive wire, and hydrogen at the negative. It is, therefore, supposed that oxygen is naturally negative, and hydrogen naturally positive; they consequently attract each other and form water, which is neutral, the electricities compensating each other. Now the union of oxygen and hydrogen arises from the operation of a certain attractive power which has always the same limit; if then, a stronger attractive power be presented, they will separate. The extremities of the voltaic battery may be rendered respectively positive and negative to any extent by increasing the number of plates. When two wires from the opposite extremities of such a battery are introduced into water, if their electrical states are more powerful than the natural electricities of its elements, these will necessarily separate, and pass to the oppositely electrified wires. The gases thus attracted to the wires will combine with them, if they are susceptible of combination; but if this is not the case, they will escape.

Thus, when the wires are formed of a metal that readily combines with oxygen, no gas appears at the positive wire, but a quantity of the oxide of the metal is gradually formed there; and it has been observed, that when tellurium is employed for the negative metallic surface, a solid compound of that metal and hydrogen is formed.

The most striking and the most common experiments are those which consist in the exhibition of the effects of the galvanic energy upon the organs of animals. If two metallic rods, or what is equally convenient, two silver spoons, be grasped one in each hand, the skin of the part being moistened with a solution of salt, and one of the spoons be brought in contact with one end of the battery, the moment the other comes in contact with the other end of the battery the shock is perceived. Fifty compound plates will give a shock which will be felt in the elbows. The shock from a hundred plates will be felt in the shoulders. A greater number of plates gives so forcible a shock to the muscles as to be dreaded a second time. If the plates be from eight to twelve inches square, the effect will be continued until the acid in the cells is expended. Several persons may receive the shock together, by joining hands, in the same manner as in receiving the shock from a Leyden phial. Their hands should be well moistened; but the strength of the shock diminishes as it proceeds, in consequence of which the last person feels it much less violently than the first.

Mr. Partington concluded his lecture by exhibiting the effects of voltaic electricity in its passage through warm, as well as cold-blooded, animals after death.

The apparatus department connected with this institution is going on with great spirit. In addition to the electrical apparatus which has been furnished for the lectures Mr. Partington has already delivered, a good collection of chemica 1 apparatus has been provided, and extensive orders have been given to the best workmen in the various branches for pneumatical, hydrostatical, optical, and magnetical apparatus. Apparatus for the illustration of the principles of mechanics have been got up, under the direction of the apparatus committee, (aided by the professional experience of Mr. Downes,) by a common carpenter: by this means a great saving has been accomplished, and the apparatus itself is on a much larger scale than if it had been obtained from the regular instrument-makers; indeed the greater part of it is peculiarly ingenious, and will form a striking feature in this institution.

[ocr errors]

THE CITY OF LONDON INSTITUTION.

The other committees have not been less active and zealous in accomplishing the various matters committed to their superintendence: and if this committee continue the same line of conduct hitherto so zealously and successfully pursued by them, we feel confident that the prosperity of the Spitalfields Mechanics' Institution will be secured.

SCIENCE AND USEFUL DISCO

VERIES IN THE ARTS.

PRESERVATION OF WATER.

Most of our readers are aware that water may be preserved in a state of freshness for a considerable time, by the addition of a little sulphuric acid (oil of vitriol.) A new mode of effecting this object at sea, has now, however, been suggested by an officer of the name of Ruyter. He recommends the use of a composition of resin and olive-oil, well mixed with brick dust, to which he gives the consistence of varnish. He renders the resin adherent by melting it with olive-oil, which unites itself with great facility to iron, with which it becomes perfectly combined when applied to it very hot; while its combination with the brick-dust gives it a sufficient degree of solidity without altering its adhering quality. This plastering, when applied to the inside of the casks, is not liable to be dissolved by water, which, on the contrary, increases its hardness, while it preserves the iron on the outside from being rusted. The author states, that he has employed this composition for several years on casks bound with iron hoops, which underwent no oxidization, and therefore rendered the use of pitch unnecessary.

PRODUCTION OF GAS IN THE MANUFAC

TURE OF CHARCOAL.

An apparatus for this purpose has been contrived by M. Mollerat. In the carbonization of wood, thirty parts only in a hundred are fixed and produce charcoal; fifteen parts are converted into gas, twenty parts consist of water in a state of steam, twenty of pyroligneous acid, and fifteen of vegetable oil, which requires no less than two hundred and fifty degrees of heat to make it evaporate.

DETERIORATION OF THE AIR BY FLOWERS.

Some interesting experiments have been performed on this subject by Saussure. The flowers of aquatic vegetables do not develope themselves in media deprived of oxygen gas; they require for

865

their support a greater proportion of this than the other parts of the plant. Some flowers, as (roses, preserve their corolla for a shorter time in the air than in vacuo or in azote; but when removed, their petals exhale an offensive odour, so that though apparently in full vigour, they have actually undergone decay. When a flower is placed under a receiver full of air confined by mercury, the volume of air is very little if at all altered. Oxygen is, however absorbed, which is replaced by its own volume of carbonic acid. Saussure has not been able to detect any hydrogen in the air in which the plants were confined, nor does there seem any alteration in the volume of nitrogen. The following are a few of the results of his experiments, with respect to the difference in the quantity of oxygen consumed by the flowers and by the leaves. The experiments were performed in summer and in the shade, and only when the flowers were fully developed.

Oxygen Oxygen Flowers. consumed by consumed by flowers. leaves.

Single gilliflower.. 11
Passiflora serratifolia 18:5
White lily........ 5
Carrot (umbels of )
Single tuberose

....

8.8

9

FUSED CHARCOAL.

4'

8.5

2.5

7.5

3

At last a specimen of fused charcoal, or supposed artificial diamond, has been examined. The specimen was obtained by professor Macneven, of New York, by means of Hare's Deflagrator; it was sent to Dr. Cooper, and by him to Mr. Vanuxem, who examined it, having always been very sceptical of the fusion of charcoal. It consisted of a large and small globule, connected together by a thread; of a black colour, without lustre, and opaque. When struck, it yielded without breaking; received a polish like that of iron; when filed, it gave way as iron or soft steel would do; it was attracted by the magnet, and when hammered was malleable. Nitric acid, when heated, acted violently on it; and ultimately, peroxide of iron and a little silica were obtained; the proportion of silex to metallic iron, being about 11 to 5. Such, therefore, is the nature of the black fused charcoal. Messrs. Silliman and Hare, however, deny that Mr. Vanuxem had operated on a proper specimen.

[blocks in formation]

Monday evening, at the London Coffee-: house, under the most favourable auspices. Upwards of seven hundred persons were present; the room was crowded to excess, and the most lively and gratified interest was expressed on the subjects of the meeting. Our limits do not admit of our relating the proceedings at length, but we intend, in future, carefully to record the progress of this promising association.

Mr. M'Culloch, who has become deservedly popular in the metropolis by his able discourses, delivered the first of these introductory lectures. He began with pointing out that, in general, in estimating the sources of national prosperity, the intelligence of the people was entirely overlooked; and yet, he asked, what but this-what but the knowledge of the people in the application of the natural means placed at their disposal, distinguished civilized from uncivilized society? The cotton manufactory, which has been said to have carried us through the late threatening contest, was entirely the creation of Arkwright, Hargreaves, Compton, and Watt. But the present rapid improvements in education, extending knowledge and intelligence to a much larger class of persons, promise us still more important discoveries, and lead us to hope that the splendid achievements of Arkwright and Watt may be surpassed, though they can never be forgotten. Thousands of individuals will now contribute to promote the progress of society, who, but for our extended education, would have gone from the cradle to the tomb without deviating from the track of their ancestors. The object of the proposed institution is to promote knowledge among the middle classes, and be for them what the other institutions now establishing in various parts of the country are for the mechanics and other operative classes. To suit them it is to be more literary than the Mechanics' Institution, and embrace a wider field of intellectual inquiry and accomplishment.

After pointing out the proposed objects of the institution, Mr. M'Culloch called the attention of the meeting to the necessity there was for the commercial classes to understand the general principles of trade and the whole theory of money. There was a peculiarity in commercial science which led to many false views. Every regulation interested a numerous class of persons in its support; and the legislator committed no error which did not give rise to a false theory. To counteract this, there was no other means but giving correct information to the middle classes, who formed the bulk of the most influential part of the community.

After pointing out to the young men assembled, the great advantages of know, ledge, and telling them, though wealth. might place them in the house of com>: mons, their relative situation there would› be determined by their knowledge, Mr. M'Culloch concluded an admirable discourse, by reminding the meeting of the late Mr. Ricardo-who began life under. more disadvantageous circumstances than most of them, and attained nearly the highest place of his wealth, and the very highest of talent and acquirement.

At the close of the lecture great numbers put down their names to join the society, which, we doubt not will meet with the most triumphant success. Indeed, an institution of the nature pro posed, we have long wished to see established, and we feel confident that the young men of the metropolis, engaged in commerce and the liberal professions, will avail themselves of the opportunity to form an establishment which will not only open to them a wide field of information connected with their respective pursuits, but afford a pleasing source of intellectual recreation. The undertaking is promoted by sir John W. Lubbock, Mr. John Smith, M. P., Mr. John Martin, M, P., Mr. Al derman Thompson, M. P., Mr. Whitmore, and several other distinguished persons of the City.

THE PROPOSED LONDON
UNIVERSITY.

MR. CAMPBELL's late letter, concerning
a London University, addressed to Mr.
Brougham, in the Times newspaper, his
subsequent disquisition on the subject in
the New Monthly Magazine, and the
successful motion made in parliament by,
the latter gentleman, for leave to bring in
a bill for such an establishment, have
excited considerable interest, not only in
the learned world, but among the public
in general.

The idea of such an institution is not founded on any alleged deficiency in the existing universities, but purely on their inconvenient distance from the metropolis, and the consequent expense of sending a young man to college.-The quantity of gold that must necessarily flow from the pockets of parents, in order that their sons may drink of the Pierian stream, is the great obstacle which is sought to be avoided. Mr. Campbell's opinion is, (and it is also ours,) that a better education might be brought within the reach of the rising race of London, than that to which their intellects have hitherto

WEEKLY CALENDAR.

been confined; he likewise thinks (and again we think with him) that this higher degree of mental cultivation should be provided for by a grand and suitable seminary in a scholastic institution, that, without going into Arabic, Hebrew, Algebra, or the higher mathematics, should furnish the mind with elegant and useful knowledge, give it the dignity and elevation natural to the light which learning bestows, and raise the moral and intellec tual character of the middling classes of society.

That this is highly desirable will scarcely be denied by any one. The rank proposed to be improved by a London University is that which forms the link between the higher and the humbler classes; the effect, therefore, of a superior education in this rank would operate in two directions: it would soften, if not annihilate, the coarse, inurbane demean our sometimes exercised by the middle orders over their workmen and dependants, and at the same time raise them to that decent self-respect which, while it imparted more of polish to their manners, would guard them against the adoptive servility towards their superiors in station; two points which, properly gained, would improve the confidence of the higher orders in the honour and integrity of their tradesmen, and the professional ministrants to their enjoy ments, and secure the comfort and kind treatment of the operative classes.

The university projected by Mr. Camp bell, and recommended by Mr. Brougham, though not unlimited in its literary and scientific latitude, is far from being intended to be confined to a loose, smatter ing kind of knowledge-to that half fledged intelligence which attains no paramount height-which leads the mind every where and no where-which presents to it a false or insufficient view of things, and tends to fill it with an over weening and egregious self-conceit-a conceit that uniformly begets a fondness for empty loquacity, and a dogmatical obstinacy, in argumentation. Though the London University is not to have the power of conferring degrees, its plan is to extend to the full and sufficient culti vation of every language and every science that shall be included in the sphere of its operation; and that sphere is designed to comprehend whatever is intellectually ornamental, or practically beneficial.

The expense of erecting a college or colleges for the proposed undertaking, has been estimated at 150,000%. "But suppose," says Mr. Campbell," it should amount to 200,000%, what would that

367

sum be to wealthy London?" We agree with him in thinking that such a sum is not worthy of being weighed against the great and durable benefits that would arise from a grand seminary for letters and science in London or its vicinity. We see on the establishment of such an in stitution, not only the certainty of a new mental elevation in the capital of England, a furtherance of that spirit for the mind's improvement, which at this moment is manifesting itself in the various scientific and mechanical societies that have recently been formed-but a surrounding diffusion of intelligence-a ramification of the same laudable ambition;—we see in it the parent of an emulative thirst of knowledge elsewhere, or the source of a degree of information in other cities and great towns, that could not but exalt the mental character of the country, and prove not only a metropolitan, but a national blessing.

These are advantages which, in our opinion, ought powerfully to press this great and liberal project upon the attention and patronage of the London pub lic. And if to the consideration of these be added that of its other various commendable features, (among which we give a high rank to its cheapness, as carrying with it an extending power of intellectual cultiva tion,) its great and important value will be obvious to every one; and all who have any pride in the nobler accomplishments of their countrymen-who look to the future honour of England, in the liberal acquirements, extended knowledge, and elevated sentiments of the respectable; if not the exalted classes of the community, will, we feel confident, think with us, that the establishment of a London University is a measure devoutly to be wished; and that its realization would be worthy the present improved spirit of inquiry and rising taste and intelligence of the British empire,

Weekly Calendar.

June IV.-Saturday. High Water, Morn. IV. 20 m.-Even. IV. 39 m, Sun rises, III.51 m.; sets, VIII. 9 m.

THE flower garden is usually in all its glory at the commencement of June, and nothing can be more delightful than to breathe the fragrance, and observe the countless varieties, which grace the parterre of Flora :

Every sense Drinks in the balmy season; every day, The pageant varies its magnificence. It does not appear that either the

[ocr errors]
« ПретходнаНастави »