« PreviousContinue »
plates, or even from other prints; and an operation introduced which might, in some cases, compete with photography, and, in others, supersede the printing-press.—Mr. Hyde Clarke; Railway Magazine.
EXPLOSION OF GUNPOWDER BY THE VOLTAIC BATTERY.
COL. PASLEY, R. E., has made several successful subaqueous and subterraneous experiments at Chatham, in firing gunpowder by means of the voltaic battery, at the distance of 170 yards. The conducting wires were nearly the whole distance either under ground or water. Large stones, prepared for the purpose, and let down 14 feet under water, were blasted in the Medway by this apparatus, some charges having been under water for a few days previous to the explosion. The conducting wires were secured to a tarred rope with hemp yarn sewed round them. It was found difficult to attach the ropes in such a manner as to avoid breaking the small platinum wire enclosed in the charge. It was also found that the force of the battery considerably depended on the distances of the objects, and the thickness of the wires used in the experiments. Conducting wires of small diameter, used for a given distance, were found to require a much more powerful battery to ignite the charge than those of greater diameter.Railway Magazine.
The details of Col. Pasley's operations against the wreck of the Royal George, at Spithead, with the voltaic battery and gunpowder, have been very successful. On Sept. 23rd, a cylinder containing 2,320 lb. of powder was lowered to the bottom, and placed alongside the most compact portion of the wreck by divers attaching to it hauling-lines rove through blocks. The vessel in which the battery was placed, was then drawn off 500 feet, which was the length of the connecting wires; and instantaneously, on the circuit being completed, the explosion took place. The most remarkable effect on the water was its uprising to 28 or 30 feet in a compact mass, from a depth of 90 feet. Neither the shock nor the sound was so great as in an explosion with 45 lb. of powder. Altogether, the Colonel has recovered from this wreck 12 guns, 5 gun-carriages, 100 beams or riders, or fragments of them, exclusive of other timbers, planks, and coppers; besides the working places and boilers complete, the stern and great part of the bows, the two capstans, part of the main-mast, and all that remained of the fore-mast, of the Royal George.
The above is but one of the many adaptations of electricity to useful purposes, during the past year. A correspondent of the Mechanics' Magazine, we perceive, proposes to light street lamps by electricity.
ELECTRO-MAGNETISM AS A MOTIVE POWER.
THE emperor of Russia lately appointed a commission to inquire into the applicability of electro-magnetism as a moving power; and from an official report by this commission, the substance of which is given in the last number of The United Service Journal, it appears that Prof. Jacobi has actually succeeded in impelling a vessel by electromagnetic power.
The vessel was of that species of galley which is well known in the
Russian navy; its measurement, 26 feet in length and 8 in width. On smooth water, it was impelled at the rate of more that 3 feet per second of time, or somewhat above 2 miles per hour; and the average of a number of experiments was from 2 to 3 feet per second. It performed a distance of rather less than 5 miles along the Neva and the town canals in about 2 hours. The space occupied by the machinery was 1 foot 2 inches in breadth and 2 feet 1 inch in length. The galvanic batteries, consisting of 320 pairs of plates, were arranged along the sides of the vessel, within which twelve persons were seated at their ease. These batteries were used several days consecutively, and did not exhibit any diminution of power. The experiments which have been made have opened out much that was unknown on the subject both of electricity and magnetism, with regard to their practical bearings, and suggested the introduction of very considerable improvements in the construction of the machinery upon a larger scale. From two to three months were consumed in the various trials hitherto made, but as yet they have not been sufficient to determine what quantity of zinc a machine will require per day to every horse-power, or how much of it will be converted into vitriol; it was ascertained, however, that the plates, whose whole weight was originally 400 lb. and superficies 96 feet square, had not lost more than 24 at the termination of the experi
An American gentleman, (Capt. Taylor,) states that he has been equally successful in applying electro-magnetism, as a driving power to machinery on shore.
ELEMENTARY LAWS OF ELECTRICITY.
MR. W. HARRIS, F. R. S., on June 20, presented to the Royal Society the Third Series of his " Inquiries concerning the Elementary Laws of Electricity;" in which he proposes to perfect the methods of electrical measurement, whether relating to the quantity of electricity, intensity, inductive power, or any other element requiring an exact numerical value; and, by operating with large statical forces both attractive and repulsive, to avoid many sources of error inseparable from the employment of extremely small quantities of electricity, such as those affecting the delicate balance used by Coulomb. The author then describes some improvements in his hydrostatic electrometer; the indications of which depend on the force between two opposed planes operating on each other under given conditions, are reducible to simple laws, and are hence invariable and certain; the attractive force between the two discs is not subject to any oblique action, is referable to any given distance, and may be estimated in terms of a known standard of weight. The author next proceeds to the elementary laws of electrical action; and proves, by experiments, that induction invariably precedes, or at least, accompanies, attraction and repulsion. Experiments also show this inductive influence to be, probably, in some way dependent on the presence of an exquisitely subtle form of matter, which may become disturbed in bodies, and assume new states or conditions of distribution. Very numerous experiments are detailed, showing the influence of changes of different intensity, of
changes in the dimensions and distances of the opposed discs, of interposed bodies of different forms, &c., on the phenomena of induction. The paper concludes with formulæ as the results of the author's investigations.-Philos. Mag.
PECLET'S NEW ELECTRIC CONDENser.
THIS new condenser is composed of three plates of glass, roughened by rubbing the surfaces carefully one upon another. They are entirely covered with gold leaf pasted on with alumine. One of these plates, A, is fixed to a common gold leaf electrometer, its upper surface being varnished. The second, B, is placed on the first; it is varnished on both sides; a small, gilt, unvarnished, copper stem is fixed horizontally at a point in the circumference; it carries in its centre, like the moveable plate of common condensers, a glass stem, which serves as a handle. Finally, on this last plate is a third plate, C, with a hole in its centre, through which passes the stem of the plate B. The plate C is varnished on the under side only, and its central orifice is furnished with a glass tube which encloses the stem of the plate B, but of a less height.
This apparatus is used as follows: we touch the upper plate with the metal whose action upon gold we wish to determine, and put the plate B in connection with the ground:-this connection is then broken, the plate C is raised, and we touch the plate A. This manœuvre is repeated a certain number of times. Lastly, by means of the stem of plate B, we raise at once the plates B and C; when the gold leaves of the electrometer diverge to a distance dependent on the number of
The cage which encloses the gold leaves is formed of parallel glass plates, and is placed on a screw tripod, furnished, on one side, with a vertical plate, pierced with a small hole, and on the other with a portion of a divided vertical circle, whose centre is at the same height as the hole of the plate and the upper extremity of the gold leaves: in looking through the hole of the plate we observe the deviation.
The following two series of experiments will give an idea of the power of this apparatus. By touching the upper plate with an iron wire, after 1, 2, 3, 4, 5, and 10 contacts, the leaves separated 9 and 2-5ths, 20, 25, 31, 41, and 88°. By touching the upper plate with a platina wire, a single contact produced but a feeble deviation, which increased to 15° after three contacts, and to 53° after 20. The experiments with platina were made by using a platina wire, which had just been reddened in the flame of alcohol, after washing the hands in distilled water. The experimenter had previously assured himself, by a great number of successive contacts, in which he touched the upper plate with a finger, that the plates did not contain any electricity.
The new fact of the development of electricity by the contact of gold and of platina, was also directly proved by means of a simple condenser of extreme sensibility obtained by giving to the coats of varnish a suitable thickness, and rendering their surfaces perfectly plane.
It is evident, from the disposition of the apparatus, that the quantity of electricity set at liberty, which causes the divergence of the leaves,
is proportionate to the number of contacts: now, it results from numerous experiments, that as far as about 20° the deviation is proportionate to the number of contacts, hence to this extent the deviation is proportionate to the quantity of electricity. It would be easy to make a table which would give the quantity of electricity corresponding to the deviations which exceed 20°, since these quantities are proportionate to the number of contacts.-Ann. de Chimie; Franklin Journal.
Mr. W. S. HARRIS, F. R. S., has communicated to the Philosophical Magazine, No. 98, an elaborate memoir "on Lightning Conductors, and on certain Principles in Electrical Science," with experiments and details, too numerous to quote.
In conclusion, Mr. Harris states as his confirmed opinion, after a long and severe examination of the laws of electrical action, and of cases of ships and buildings struck by lightning;-that a lightning rod is purely passive; that it operates simply in carrying off the lightning which falls on it, without any lateral explosion whatever. Mr. Harris does not, however, deny the general inductive effect mentioned by Lord Stanhope on bodies opposed to the influence of the thunder-cloud, and that the displaced electricity will again find its equilibrium of distribution, and return to those bodies, which effect would necessarily take place, whether we had a lightning conductor or not; an additional reason for linking the detached conductors in a ship's hull into one great mass, so as to have as few interrupted circuits as possible in any direction: this opinion Mr. Harris is prepared to substantiate by striking cases in which ships have been struck by lightning.
GAUSS ON THE THEORY OF MAGNETISM.
IN our theory it is assumed that every determinate magnetized particle of the earth contains precisely equal quantities of positive and negative fluid. Supposing the magnetic fluids to have no reality, but to be merely a fictitious substitute for galvanic currents in the smallest particles of the earth, this quality is necessarily part of the substitution; but, if we attribute to the magnetic fluids an actual existence, there might, without absurdity, be a doubt as to the perfect equality of the quantities of the two fluids.
In regard to detached magnetic bodies, (natural or artificial magnets,) the question as to whether they do or do not contain a sensible excess of either magnetic fluid might easily be decided by very exact and delicate experiments.
In case of the existence of any such excess in a body of this nature, a plumb-line to which it should be attached should deviate from the true vertical position in the direction of the magnetic meridian.
If experiments of this kind, made with a great number of artificial magnets, and in a locality sufficiently distant from iron, never showed the slightest deviation, (which we should rather expect,) the equality of the two fluids might, with the highest degree of probability, be inferred for the whole earth; though, without wholly excluding the possibility of some inequality.-Taylor's Scientific Memoirs, vol. ii. (part vi.) p. 228.
ON May 7 and 27, Prof. Daubeny explained to the Ashmolean Society certain views with respect to the Constitution of Matter and the laws of Chemical Combination, which had been brought forward within the last few years. He showed, that although matter may consist of atoms, yet chemical union must be supposed to take place between groups or assemblages of such atoms, and not between the individual atoms themselves. He then showed, that the bodies which are to be regarded in the light of elementary substances, in the case of vegetable or animal matter, are themselves compounds, consisting of carbon, nitrogen, hydrogen, and oxygen; and, on the other hand, that the chemical properties of those bodies, which, as far as we know, are simple, admit of being modified very considerably by electrical and other agencies. He likewise pointed out that several distinct chemical compounds may exist made up of the same elements, united in the same proportions; and, on the other hand, that simple as well as compound substances assume various distinct crystalline forms, according to the circumstances under which they happen to become solid.
Dr. Daubeny next explained the doctrine of Catalysis, or the influence which certain bodies exert in producing chemical changes, without entering into combination with either of the constituents of the compound substances which they decompose. This doctrine was illustrated by the action of spongy platinum in kindling hydrogen gas, by the conversion of starch into gum and sugar under the influence of diastase or of sulphuric acid, and probably in the process of fermentation produced in saccharine matter by the presence of a minute proportion of gluten. He next pointed out a species of attraction which seems to operate amongst homogeneous masses of matter, as cohesive attraction does amongst their particles; and which he proposed to distinguish by the term adhesive attraction. It is by virtue of this force that portions of flinty matter disseminated through a mass of clay, become gradually collected into lumps or nuclei. He then noticed the new views of Prof. Graham of London, who has shown that water acts an important part in the constitution of acids, salts, &c., and influences their chemical properties no less than their crystallization. He concluded by observing that it was probable that the various products of animal and vegetable life result from the operation of these and other similar natural laws, which pervade the organic as well as the inorganic kingdoms; and that many of the compounds hitherto obtained exclusively from the processes of living matter may be created by artificial means. Two or more of these compounds have been already produced by chemists of the present day.
Dr. Daubeny having, in the course of his paper, alluded to the new