wires of the two magnets were united at one of their extremities so as to form one continuous wire, and the voltaic current was passed from the same pair of plates, through the thick wire coiled on both magnets. The shock given by the thin wire, in this case, (on breaking battery connexion) appeared to be twice as strong as the shocks given by either of the magnets seperately. Hence, if the thin wires coiled on any number of electro-magnets, be united together so as to form one continuous wire; and, if all the magnets be simultaneously magnetized by the voltaic battery, an electric current will be produced in the thin wire (at the moment of breaking battery communication) having an intensity equal, or nearly equal to the sum of the intensities of the currents excited in each of the helices. Care must be taken to unite the thin wires in such a manner, that the electric current excited in the helix of each magnet on breaking battery communication, may all flow in the same direction; otherwise, the current produced in the helix of one magnet may neutralize the current excited in the helix of another. From a small electromagnet, an electric current equal in point of intensity to that of a battery containing 1,000 or 2,000 voltaic circles, may be readily obtained. Hence, by means of 100 electromagnets, and a battery containing 10 or 12 large plates, we may produce an electric current equal in point of intensity to that of a battery containing 100,000 or 200,000 pairs of plates. An electric current of enormous intensity may be also obtained from a single magnet of very large size. But, I am strongly inclined to think that the electric power of 100 small magnets is considerably -greater than that of a single magnet equal in size to the 100 magnets. First, because all long bars retain a considerable portion of the magnetic power imparted to them by the voltaic current. I have tried about fifteen bars of iron, varying in length from 6 to 13 feet, and every one of them retains some of the magnetic power. Our large electro-magnet retains constantly a power capable of lifting about twenty pounds. Secondly, because long bars lose their magnetism, slowly and not in an instant.

Any number of electro-magnets for electrical purposes, may be united so as to increase those effects which depend on quantity of electricity. If the similar ends of all the thin wires coiled on the magnets be connected together, while the similar ends of the thick wires belonging to the magnets are connected with the battery, as many electric currents will (at the moment of making and of breaking battery cammunications) be excited in the thin wires as there are mag

nets, and will pass through any body placed between the ends of these wires.

1 have just made an electro-magnet which, with a single pair of 7 inch plates, gives (even at the moment of making battery communication) a shock as strong as the shock from about thirty ar forty pairs of plates.

In making electro-magnets which are to be connected for the purpese of obtaining increased electric intensity, care must be taken not to solder the thin to the thick wires of the magnets, and to leave both ends of the thin wires projecting.*

About four month ago I coiled on a cylinder of wood about 10 feet of covered copper wire one-eighth of an inch thick. Over this wire, I coiled about 200 feet of very thin wire which was also covered. When the ends of the thick weke were connected with a pair of plates, a shock was received by holding in the hands a pair of cylinders connected with the ends of the thin wire. This shock was felt only at the moment of making battery communication, but not on breaking the communication. When the voltaic current was passed through the thick wire from a battery of 20 pairs of 2 feet plates, there was no shock on breaking communication, but, on making communication, the shock was very strong. The electric current which gave the shock was incapable of producing any effect on a very delicate galvanometer. When an iron bar was put into the helix formed of the thick wire, the shock felt on making communication was greatly increased, but was far weaker than the shock received on breaking communication.

In a paper published in the July number of the Annals, I stated that I was then employed in making an electro-magnetic engine to be worked by 26 electro-magnets. In the end of June, 1 tried the engine before it was completed, and found these two defects in it. The first was that some of the magnets were connected by iron where they ought to have been connected by a substance not susceptible of magnetism; the second arose from the number of magnets which were divided into two sets, each containing 13 magnets. I found it impossible, in the plan which I adopted, to make an odd number of magnets work, and was therefore

For the illustratiou of secondary currents at the lecture table, I find no method so simple and explanatory, as by having two distinct coils, each on its own bobbin. The battery coil of thick bell wire is on the smaller bobbin, and can be introduced to the interior of the thin wire coil at pleasure; the bobbin of the latter having a hollow axis sufficiently large for its admission. By this means it is obvious to every auditor, that the battery current has no communication with the outer coil. EDIT. ANNALS OF ELEC.

The

obliged to reduce the number of magnets to 24: or to two sets each containing 12 magnets. I also substituted a brass connexion between the magnets for the iron one. I then found that one small electromagnet was capable of producing circular motion in a wheel which weighed about 100 pounds, and that six magnets were sufficient to give rapid motion to the wheel. results of the experiments which I made, convinced me that electro-magnetism might be successfully applied to the working of machinery of every kind, and I resolved to get made an engine which would do the work of one horse or perhaps of two. This engine will contain 40 electro-magnets, and I expect that, with a battery containing 6 square feet of zinc, it will propel, at the rate of seven or eight miles an hour, a carriage which along with its load, will weigh 13 cwt. The engine will be ready for work in the end of this month or in the beginning of the next. By calculations founded on experiment, I have been led to the following conclusions. First, that an electro-magnetic engine as powerful as any of the steam engines on the Kingstown Railway, may be constructed for the sum of 2501.; secondly, that the weight of such an engine will not exceed two tons; thirdly, that the annual expense of working and repairing it will not be more than 3007. If my calculations be correct, the expense of propelling the railway carriages by electro-magnetism, will be scarcely one fourth of the cost of steam. I have found that the first cost of an electromagnetic engine, and the expense of working and repairing it, increase only as the square root of the power of the engine. Thus, the first cost of an engine of 100 horse power, aud expense of working it will be very little more than ten times the cost of an engine of one horse power. A battery containing 10 square feet of zinc will work an engine 100 times as powerful as that which requires only one square foot of zinc. N. J. CALLAN.

Maynooth College, September 11, 1837.

motion on one end of the column and communicating it to the other. To each end of a column he attaches a float board with an index, and depression of any given number of figures on one index, will be immediately followed by a corresponding rise of the float board and index at the other end. It is supposed that this simple longitudinal motion can be made to convey all kinds of information. It appears to us that the amount of information which can be conveyed by the motion in one direction only, of the water, or backward and forward, must be limited. To make the mere motion backwarks and forwards of a float board, indicated on a graduated index, convey a great number of words or letters, is the difficulty to be overcome. Mr. Whishaw has exerted his ingenuity in this way, with a promise of success, and by-and-bye, the hydraulic telegraph may supersede the semaphore and the galvanic telegraph.-Courier.

THE CUBA RAILWAY.

We have been furnished by a correspondent with the following account of the railway which has been constructed across the island of Cuba by the government of that island, and which is about to be completed and opened in a very short time :

This railway passes from the city of Havannah to the port of Batabano, on the southern side of the island of Cuba, and is eighty miles in length. The purpose for which it has been constructed, is to connect the commerce of the Havannah and the northern side of the island, and also the commerce of New Orleans and various other important parts of the northern side of the Gulf of Mexico, with the West India islands and the Spanish Main. Cuba being an island of upwards of 700 miles in length, but only about 80 miles in its average breadth, and lying in a position which requires vessels from the north or the south to sail round it in order to reach the opposite sea, it was projected by the present governor of the island, that a railway should be formed for the purpose of cutting off a navigation of several days, by passing across the island from north to south. It is therefore apparent that the railway is a work of the most important kind, and will tend to improve most materially the commerce, not of the island of Cuba alone, but of the English West India islands, and of all the countries of the West India seas.

island, for the purpose of taking in some very rich and populous villages and sugar plantations which exist upon the way. This deviation, however, will serve as a branch, should the traffic upon the railway prove equal to the expectations of the government, and the course, at a future time, be required to be rendered perfectly direct from sea to sea.

Fifty miles of the line have been completed some months since, and a steam locomotive engine, of great power and size, has been mannfactured for it, by the Messrs. Braithwaite, of the New Road. The whole of the levels and other more important works upon the remaining thirty miles, are now also completed; and the rails having been shipped from England about two months since, it is expected that the next arrivals from the Havannah will communithe intelligence of the opening of the entire line.

Seeing that a railway of so great a magnitude is thus about to be completed, in so comparatively improbable a situation as the island of Cuba, let us hope that the governments of the neighbouring English West India Islands will profit by the spirited example of the Spaniards, and proceed to construct similar works in many localities amongst the islands, where outlays of money for such purposes would be much more certain of being repaid than in any of the colonies of Spain.-Railway Times.

NOTES AND NOTICES.

German Railroads.-The operations on the Leipzig and Dresden railroad have been carrying on with great vigour, but it remains to be seen whether they will be affected by the sudden disappearance of the secretary, Mr. Tenner, who, since the beginning of the present month has vanished. During September, the number of labourers employed on the works was no less than 5887. The line is open from Leipzig to Althen, and during September, the number of passengers, on twenty-two travelling days, and in 198 journeys, amounted to 16,577 persons from Leipzig to Althen; and 15,597 persons from Althen to Leipzig, altogether 32,174 persons. Up to the 30th September, there had altogether been 94 travelling days, and 802 journeys, and 100,655 persons had been conveyed both ways. The locomotives have arrived in readiness for the Potsdam railway, but it is said, that competent judges affirm that whatever exertions may be made, at whatever expense, it will not be ready to open in less than three years.

East Indian Caoutchouc.-It is well known that a large supply of this valuable substance might be procured from India, if the same care were to be

"The

taken in gathering it as in South America. London Caoutchouc Company," impressed with this idea, accordingly sent to India an offer of a premium of fifty pounds for the first hundred weight of East India caoutchouc which should be shipped for England. When the offer arrived, however, it was somewhat of the latest; the great demand existing at home for the article had been previously heard of, and large quantities were already on shipboard, compared to which the "hundred weight" stipulated for was but a molehill to a mountain ! The whole affair forms an apt illustration of the doctrine that, in commerce, the force of self-interest is far superior to that of artificial bounties.

of

Specimen of French Invention.-Among the new joint-stock companies which are starting up thick and threefold in the French capital, there is one of rather a more novel character than usual. This is a "Navigation Company," which proposes to introduce into France those improved methods of communication in which, as the prospectus observes, she is far behind many other countries, but more especially England and America: to effect this object, or even to go beyond it, it is proposed to build a number of steam-towing vessels, some of a large size for the open sea, and others of smaller dimensions for the French rivers, with an immense fleet of ships and barges to be propelled by the former. The grand feature of the scheme is, that these vessels are to be so constructed as to serve the purposes conveyance by land as well as by water: the towing ships, when required, are to mount the railways as locomotives, while their convoy are to follow in the character of a " train." The worst of the matter is, thst the projectors of the plan do not point out in what way the necessary metamorphosis is to be effected: they content themselves with dwelling on the great and numerous advantages of their scheme, but do not so far "condescend upon particulars" as to give even an inkling of the method of putting it in practice. They appear to have been too well satisfied with the brilliancy of the idea, to trouble themselves in the least as to the practical details. Their prospectus is headed with a wood-cut representing a couple of steam-vessels, with nothing remarkable about them, towing along a number of boats and barges, and underneath the public are informed that they are to do duty by land as well as water,-but that is all, The projectors probably think it will be time enough to have their vehicles ready for the railroads, when the railroads in France are ready for them! Meanwhile, provided they can raise sufficient capital, they propose forthwith to commence operations by starting a line of boats on the Upper Seine, from Champagne to the capital, and another on the Lower Seine, from Paris to Rouen, as well as a sea-line, from Havre (to begin with) to London, Antwerp, and Amsterdam. The foreign vessels are intended to set out three times a month, and the domestic every other day. There is no doubt, whatever may be the fate of the present project, that the improvement of internal communication, especially by the agency of steam, is daily making a rapid progress in almost every part of France.

London and Brighton Railway without a Tunnel. -We understand the original Shareholders on this line have given the requisite notices of their intention to apply to Parliament this session; so that, after all, there appears some probability that this long-contested question will again be agitated-Railway Times.

HAWTHORN'S PATENT RAILWAY

PROTECTOR.

To clear the rails from impediments is of the utmost consequence in railway communication. With the railway protector affixed to locomotive engines now in general use, a necessity exists of keeping it about two inches above the rail. This is a matter of regret, inasmuch as the efficiency of the protector in the removal of dangerous impediments, accidentally or designedly laid in the track of the engine, is thereby greatly depreciated. The reason for allowing two inches between the protector and the line of road is obvious. The protector being firmly fixed to the engine, that space is necessary to prevent the appendage from coming in dangerous contact with the rail, from the undulatory motion of the machine, often increased by irregularities of the railway; and is case of a close proximity between the line of way and the protector, in those occasional instances where the end of a rail has started up at a joint, or in passing the points of a crossing, the appendage now in use, so far from conducing to safety, would absolutely increase the danger. It is therefore desirable that some plan should be adopted, which, whilst it is made to run so close to the rail as to sweep off small as well bulky substances, will give way on coming in collision with such impediments as cannot, or ought not to be removed. The subject has, by several engineers, been deemed of sufficient importance to engage their attention, and to accomplish the desired object, the after described arrangment has been designed, and recently patented by Mr. W. Hawthorn, of Forth, Newcastle. It

will be seen that a protector on this arrangment could not be firmly fixed to the frame of the engine; it is, on the contrary, connected to it by a joint, with a spring pressure upon it, thereby enabling it to move back and rise when it may chance to come in contact with such an object as started rail, as shown in the sketch. When such object is passed, the action of the spring would immediately place the protector in its former position, and enable it to remove from the rail all loose substances.

Explanation of the Engraving.

A is the-front end of a locomotive engine; B the protector, connected to the frame of the engine, by the joint C,

on which it works; D is a guide for the back part of the protector to slide in; G a steel spring connected to the protector by the link E, by which it is pressed down with a force requisite to give to it a sufficient firmness to remove any loose obstruction from the rails; I is a joint in the protector, by which it clears any impediment when the engine is moving backwards.

ETTRICK'S IMPROVEMENTS IN THE MARINER'S COMPASS-ARTIFICIAL HORIZON, ETC.

SIR, With a few solitary exceptions, the attempts at improvements on nautical apparatus, promulgated by landsmen, are altogether worthless; and this arises not so much from a want of ingenuity in the projectors, as from a total absence of that familiarity with the seamen's business and habits, which can alone lead to a right understanding of real deficiencies.

Of this truth, abundant proof might be gleaned from the pages of the Mechanics' Magazine, but what more immediately directs my attention to it at present is, the drawing and description of "Ettrick's Improved Mariner's Compass," which appeared in your 737th number. By this instrument the inventor proposes to effect a mechanical correction of the magnetic variation, and he sets out with an expression of surprise, almost amounting to scepticism, that the old compass should have been so long used, not only in the merchant service, but also in the royal navy; now, one would think, that that very circumstance, coupled with the fact that such a very simple alteration had escaped the penetration of Mr. Barlow, and others, who have devoted such close attention to the subjects, would on the contrary, have led Mr. Ettrick rather to distrust the utility of his project.

Mr. Ettrick evidently supposes that the correction for variation is made by the helmsman in the act of steering; for upon this supposition alone, could the proposed alteration be useful: but this is never the case, the steersman need know no more of variation than the wheel in his hand, he keeps a course according to the orders he receives from his superior, and in the determining of that course many elements of correction must be taken into consideration, such as currents, lee-way, &c., the simplest of all