that this application would excite all the interest of the minister of war, and of that of the marine especially; for the bullets alter so rapidly at sea, that their dimensions are soon modified in such a manner as to be prejudicial to the truth of the aim and to the duration of the pieces. It deposits a zinced bullet on the bureau.

In fine, the zincing of iron and of cast iron are of great importance to architecture and the arts of imitation. Every one knows with what promptitude the nails and bars of iron employed in buildings become oxydized, and consequently lose their tenacity; and we all comprehend to what extent it is useful to preserve, with an eye to cheapness, all the pieces of iron disseminated in the walls of a building, for they are destined to give it a solidity which will become thereby durable and susceptible of being calculated with precision. In the same manner, grates and balustrades of cast-iron, receiving a coat of zinc in place of one of paint, which requires frequent renovation, will be thus found better guaranteed against the action of water or air.

It is especially desirable that these new means are called into use to preserve statues of cast-iron, of which we have recently seen the attempt in several of our monuments, and which, in some cases, have been submitted to the application of plasterers or painters, very ill calculated with regard to science, and with an effect very deplorable in reference to art.

The processes of M. de Ruolz for zincing may be applied not only on objects small and open, but it will be possible farther to make use of them for monuments in their place, and of large dimensions, by taking some precautions easy to foresee.

Your Commission is far from having sought to enumerate here all the applications which this new means of the zincing of iron is susceptible of presenting; it has limited itself to those most essential, but they will very well suffice to make the Academy appreciate all the extent of the works of M. de Ruolz on this point.

Before quitting a subject so important, we will recall to mind the fact, that M. Sorel, on one hand, and M. Perrot, on the other, had already attained the art of covering iron with a coat of zinc by means of the pile, but still using, in all cases, solutions altogether different from those which M. de Ruolz believes to be preferable, and which have enabled him to act with economy, a point which is here truly important.

M. M. Sorel and Perrot have even announced, on this occasion, that they occupied themselves on the general problem of fixing the metals one on the other; we will hope, that by making known their processes, they will add to the perfection of an art which already appears so far advanced.

The Academy will see, with the highest interest, an industrial art destined to spread itself in the world under all its forms; to put to profitable use the pile of Volta, which had not hitherto been

industrially applied except at the metallurgic works of our colleague, M. Becquerel, and to galvanoplastik processes.

By the variety of his applications, M. de Ruolz gives to the pile an opportunity of multiplying itself and of spreading, which will become, we doubt not, a very certain cause of perfecting, both as to the construction of this apparatus, and as to the means of rendering it economic.

In conclusion, your Commission thinks itself obliged to declare that, forced as it has been to limit the time which it could consecrate to this examination, since it acted as a Commission for the prize Montyon, and as it could no longer withhold its report, it was bound to limit itself to trace here the summary history of these experiments, without pretending to make a systematic exposition of the state of the science on the point on which it has been occupied.

That which it has had in view is the economic application of it. All its researches have been in this direction: this was its duty.

Under this aspect, the experiments of M. de Ruolz have presented it with a character really novel. Their utility has appeared to him to be worthy of all the attention of the Academy. The Academy will be pleased to recollect also, that the author of these experiments has given proof, in this long work, of a remarkable penetration, and of a perseverance worthy of being crowned with complete success.

The Commission comes, then, to demand of you to decide with confidence that the memoir of M. de Ruolz be admitted to form a part of Recueil des Savants etrangers.

But it would require still more of you-and that in the view of public interest easy to comprehend to decide that a copy of the present report be addressed to M. M. the Ministers of War, of Marine, of Finances, of Public Works, and of the Interior, who will be enabled therein to find tokens of a nature to interest the services of which the high direction is to them confided. The conclusions of this report are adopted.

On the Powers of Large and Very Small Horse-shoe ElectroMagnets. By C. H. PFAFF, of Kiel.*

So long as the hope exists of bringing electro-magnetism into use as a motive power, there will be an interest instilled on experimental enquiries respecting the determination of the most favourable circumstances for the production of still more powerful electro-magnets. With the exception of the powerful electro-magnet described by the

* Poggendorff's Annalen der Physik and Chemie. Band. 52. s. 2. 1841.

American philosophers, Henry and En-Tyck, the lifting power of which was 2063 lbs., whilst its own weight was only 60 lbs., its length being 30 inches, when bent, and the diameter of the iron 3 inches, I am not aware of any being known in Europe whose lifting power exceeded 600 lbs. By the assistance of our skilful University Mechanic, Cramer, I find myself in possession of an electro-magnet, which, by the application of a powerful voltaic apparatus, not only suspends 900 lbs., but, what to me is the main point, I am thus also in possession of an apparatus which affords great facilities in comparing the lifting powers of electro-magnets under a great variety of circumstances. Indeed, the apparatus can be so arranged as to determine the differences to 0.001, nay, even to 0.0005 of the lifting powers, however great.

The apparatus, by means of which the lifting powers of the electro-magnets were ascertained, consisted chiefly of a lever, the length of whose arms was as one to ten; it was made of iron, and supported between two stout vertical pillars, the lower ends of which were morticed into a stout base-board, to which they were firmly fixed by means of additional spurs. It was supported by an iron wedge, with its sharp edge upwards, and which served for the fulcrum. This fulcrum was fixed to the pillars about half way up, so that the lever could play freely between them. To the extremity of the long arm of the lever was suspended a scale-board for the purpose of placing the weights upon; and the cross pieces, or ankers, that were employed, were attached to the short arm of the lever, the electromagnet itself being fixed with its poles upwards. There were also some other appendages to this apparatus not necessary to describe in this place.

The large electro-magnet was so contrived that its influence could be easily ascertained under a great variety of circumstances. It is of soft iron, bent into the horse-shoe fashion. Its length outside is 3 feet 4 inches, and its mean length 3 feet 27 inches. It is formed of a cylindrical bar, whose diameter is 1 inch and 11 It is of less diameter than the American electro-magnet in the proportion of about 2 to 3. Its weight is 32 pounds, and its branches are separated from each other to the distance of 2 inches 11 lines.

lines.

This electro-magnet is covered with 60 feet of copper wire, of the thickness of 2 lines, every 10 feet of which weighs one pound. It is wound round the magnet in six equal portions of 10 feet each, which form six distinct. coils, three on each branch. Each extremity of these wires is furnished with a copper cup for holding mercury, by means of which, and short copper connecting wires, the coils can be so connected with each other and with the battery, that the current can either be divided into six distinct streamlets, one through each coil, or it can be transmitted entire and without division through the whole 60 feet length of wire constituting the coils. In the latter case, on account of the increased length of the

conductor, the resistance is proportionally greater, and the current consequently feebler: not, however, in the bare relation of the various resistances amongst the wires themselves, but must become so in the relation of these resistances with regard to the whole resistance offered to the current.

It is obvious that this arrangement of the electro-magnet at once affords the means of examining the effects of the currents when in operation on various parts of the iron. The electromotors employed in the following experiments were the well-known spirals of copper and zinc, the surface of each plate being 176 square inches, or the whole voltaic surface something more than 1 square feet. The exciting liquid consisted of water with of acid; half of which was concentrated sulphuric, and half aquafortis.

The spiral wires that surround the magnet are numbered from 1 to 6, commencing at that nearest to the end of one of the branches, and proceeding round the series, numbering them in succession to the other end; so that Nos. 1 and 6 are those spirals nearest the ends poles of the magnet, and Nos. 2 and 5 are those which occupy the middle places on each branch.

The first series of experiments with this electro-magnet were made whilst its ends were perfectly flat and smooth; so that the whole of both surfaces came into close contact with the flat smooth face of the cross piece, to which it clung by attraction. In the second series of experiments, the electro-magnet had its ends rounded in such a manner, that the flat face of the cross piece, when in contact with, and joining both poles, was a tangent plane to the curves into which the ends of the magnet were formed; and we shall presently see, with astonishment, the increase of lifting power gained by this means.

Experiments with the Flat Smooth Poles of the Electro-Magnet.

1.-One spiral electromotor brought a maximum of lifting power of 298 pounds.

2. Two spirals, as an electromotor, of double the former surface, produced a maximum of lifting power of 3684 pounds.

3. Three spirals, as an electromotor of three times the first surface, produced a maximum of lifting power of 488 pounds.

4.-Three spirals, as a small battery, of three electromotors; each of which operated as a simple surface. Maximum of lifting power, 3084 pounds.

5.-One spiral, as an electromotor, and the current transmitted through only half of the coils, viz., those three which were placed on one branch or shank of the magnet. The lifting power was 88 pounds.

6.-One spiral as an electromoter, and the current transmitted through coils 1, 5, and 6. Lifting power 584 pounds.

7.-Three spirals united into one, as an electromotor, with three times the first surface. The current, instead of being transmitted through the whole length of the coil wires connected in sequence, or end to end, was transmitted through each coil separately, or as a distinct conductor; so that each coil carried 1-6th of the whole flood. The lifting power was 98 pounds.

8.-One spiral as an electromotro: the current distributed as in experiment 7. Lifting power 28 pounds.

9.-One spiral as an electromotor, and the current transmitted through coils 1 and 6, each conducting one-half. Lifting power 981 pounds.

10.-One spiral as an electromotor, and the current transmitted through coils 2 and 5, or the middle coil on each branch of the magnet; each coil carried half the main current. Lifting power 88 pounds,

11. Electromotor as in two preceding experiments, and current transmitted through coils 3 and 4, or those farthest from the poles of the magnet. Each coil half the main current. Lifting power, 78 pounds.

12. Three spirals, as three electromotors, were employd in this experiment, and the lifting power at the first was 2984 pounds. After the connections had been continued for some time, and without disturbing the exciting acid solution, the lifting power fell to 228 pounds. When the three spiral electromotors were connected so as to form one electromotor of three times the surface of each, the lifting power was 150 pounds; and after the circuit was opened, the magnet still carried 78 pounds.

13. Three spirals, as three elements for an electromotor, were employed, The connections were such that each coil conducted of the whole current. The magnet, in one trial, would not carry the cross piece with the steel yard or lever, and, in another trial, not 28 pounds.

14. When the currents from these three spiral electromotors were conducted through the coils in such a manner that Nos. 3 and 4 carried, Nos. 2 and 5 carried, and Nos. 1 and 6 carried of the whole, the magnet would not carry the anker or cross piece. 2.-Experiments with the Electro-Magnet, when its ends or poles were rounded.

15.-One spiral as an electromotor, and the current transmitted through the whole 60 feet, from end to end, of the coil wires. Lifting power, 618 pounds.

16. Two spirals as one of double surface. 8784 pounds.

The lifting power

17. Three spirals, as one of three times the first surface, produced a lifting power of 8184 pounds.

18. The same three spirals, as three electromotors (as a smal battery), produced a lifting power of only 568 pounds.