unmoored and turned again, is very tedious, and, consequently, expensive. It consists in placing large magnets at such a distance from the binnacle, or other compass, that their attraction is equal to the deviation occasioned by the magnetic influence of the vessel. Mr. Payne's plan allows the whole arrangement to be executed in the work-shop; and the invention comprises an entirely new method for the circulation of the magnetic fluid. The inventor, it appears, collects and fixes a vast quantity of magnetism in his binnacle, and causes its influence to ascend in a conical direction towards the centre of the compass needle. The magnetism of the iron vessel is attracted to this magnetic arrangement, which cuts off a direct communication between the needle and the vessel, and leaves the needle as free to act correctly on board the vessel as on shore. The magnetic binnacle swings on substantial gimbals within an outer binnacle, covered with the usual brass top, lamp, &c. The saving of expense by this new plan will be considerable, and it will not be liable to an objection, which is advanced against Professor Airy's plan, that the compensation is not lasting. It has been found that a variation in compasses, compensated on the Professor's plan, arises by the iron of the vessel losing some of its magnetic strength by gradual oxydation, paint, &c.; while the large compensation magnets remain in preservation, and, after having been exactly powerful enough, become too powerful. The compensation power of the "magnetic binnacle," on the contrary, cannot be too powerful, but may be not sufficiently so, a defect which is soon seen, and can, of course, be easily remedied.-Liverpool Albion.

MAGNETISM AND THE WIND.

ON April 16, was described to the Wernerian Society, a Magnetical Instrument, invented and constructed some years ago by Mark Watt, esq., of Edinburgh, which, while standing upon a table in any room, and secluded under a glass shade, points in the direction of the wind. This instrument is formed of a thin bar of wood, 3 or 4 inches long, which traverses, like a compass, upon a steel pivot, by means of an agate capsule inserted into the wood. Three or four magnets are affixed to one end of the bar of wood, which has a slit one-third of its length to receive them. They are placed in a line, at a distance of half an inch from each other. The magnets are very light, being pieces of the main-spring of a watch, made straight, of different lengths, increasing from one inch to three. They are fixed quite perpendicular to the horizon, and therefore deprived of polarity, with all the south poles uppermost, and north undermost. The instrument is not a perfect vane; for although the bar of wood stands exactly according to the direction of the wind, it is indifferent to it which end turns towards the point the wind blows from. Yet several rather interesting deductions in physical science can be drawn from it. It evinces the connection between magnetism and electricity. It also renders it probable that our variable winds are caused by

electrical currents, as this instrument anticipates the changes of the wind by a quarter or sometimes half an hour.-Jameson's Journal, No. 65.

SUBDIVISION OF TIME.

MR. OSLER proposes to apply the principle of the Vernier to the Subdivision of Time, by having a pendulum, which should make, say ten swings, in the time that the principal pendulum makes eleven; furnished with a small dial, and so placed as that the coincidences, or want of coincidence, could be observed. The strokes of such a pendulum being counted, the time of every observed stroke of it, reckoned back from its coincidence with the principal, or seconds' pendulum, would, it is obvious, be found in tenths of a second.

ASTRONOMICAL CLOCKS.

PROFESSOR BESSEL, of Königsberg, has read to the British Association an important communication on an Astronomical Clock.

Having ever been of opinion that that indispensable instrument to the astronomer, a Transit Clock, could only acquire perfection if the pendulum-separate from the whole of the works were made to vibrate in equal time, whatever the temperature and the arc might be, Prof. Bessel gave some hints on this subject. After noticing Mr. Frodsham's ingenious contrivance of an isochronal piece, to compensate for the variation of the arc, he said, supposing that contrivance had been successful, there would be no more any difficulty in making the rate of the pendulum independent, as well of the vibration of the arc, as of the heat. He would submit, whether the expeditious method of coincidences might not be employed for checking the pendulum in both respects.

The pendulum, apart from the clock, being suspended from the wall, a clock, taken out of its case, might be placed before it at a distance of 6 or 8 feet; an object-glass of 3 or 4 feet focal length might be placed between both, so as to produce, exactly at the lower end of the pendulum of the clock, an image of the lower end of the other pendulum. Then the coincidences of both might be accurately observed, by a telescope placed at a convenient position for seeing both. Similar contrivances had been described in an account of some pendulum experiments made at Königsberg; and the accuracy of the method was such, that the relative rate of both pendulums might be ascertained with sufficient accuracy in a short time-in from 10 to 20 minutes. The rate of the pendulum was to be tried at different temperatures, being placed in an open box, covered at the lower end with glass, and so fastened to the wall that the pendulum could swing within it. Two metal tubes should be passed through the box, and might be heated with water or steel, so as to heat the air in the box. Previously to heating it, the air should be deprived of its moisture; and two or three thermometers placed in different situations in the box, showed the heat to be pretty uniform. Then, if the pendulum were swung before and after heating, it would be easy to ascertain the rate, and compen

sate for the heat. Prof. Bessel believed that not only the readiness with which both these experiments might be made, but also the perfect isolation of the pendulum, would recommend this method to artists and astronomers; and he had been desirous to try it himself, but had been prevented by delay in the construction of a pendulum provided with Mr. Frodsham's isochronal piece. In the construction of the pendulum, attention should be paid to one thing which seemed to have been much overlooked. It often happened that chronometers affixed to the top and bottom of a clock-case, when it was evident that the compensation was acting only below, would not compensate for the variation of the whole. He should prefer, for this purpose, the gridiron to the other form of pendulum, especially if we began as low as possible below the point of suspension, and endeavoured to carry it on to the centre of gravity. He should prefer the several rods to be of equal diameter, and to act uniformly. Perhaps, the application of galvanism, which Mr. Dent had so beautifully applied to coating spring pendulums with gold, would best answer the purpose.

Supposing the spring perfectly regulated, as well with respect to the heat as the arc, only one cause would interfere with regular vibrating times. This was the effect of that quality of the air which depends on the variations of the height of the barometer; and the other part would depend upon the variations of the thermometer, and the adjustment of the compensation for heat, There was a possibility of compensating the former by fastening a barometer tube to the pendulum, and it would not be difficult to find the suitable diameter of the tube; but Prof. B. was aware that this complication of the pendulum would be rather inconvenient. At all events, the variations of the barometer were not very great, especially if the compensation of the pendulum were made as great as possible. He submitted these hints to those celebrated artists whose admired works had greatly contributed to the promotion of astronomical purposes, and the determination of the longitude.

Sir John Herschel observed that by Prof. Bessel's plan of compensation, the use of vibration was brought within a short period of fifteen or twenty minutes, which, according to the ancient modes of determination, would have taken a whole day.

DENT'S STEEL CHRONOMETER BALANCE-SPRINGS.

MR. DENT has further reported (see Year-Book of Facts, 1842, p. 96) to the British Asssociation,-respecting his Steel Balance-spring, coated with pure gold by the electro-metallurgic process; also of the performance of his clock, in which the impulse is given to the pendulum at or near the centre of percussion. By this contrivance, he proposes to obviate the difficulty occasioned by the oil freezing at low temperatures. The stopping of clocks at very low temperatures has induced the Astronomer-Royal to invent a new escapement, which seems to answer all the conditions required; an addition of twelve pounds can be added on to the weight of the clock, and yet a variation is produced in the arc of vibration amounting to only five minutes,

while an addition of one pound to the weight of the ordinary Graham's escapement makes a difference of fifteen minutes; by Mr. Airy's plan there is always, (if the term might be used,) an extra reservoir of force; keeping the train of wheels always up to their work, and capable of overcoming the resistance occasioned by the freezing of the oil.-Athenæum, No. 766.

Mr. Dent's Improvement of the Compensation-balance chiefly consists in the two compensation-pieces being formed into curves, which have a uniform and, at the same time, a double action, without occasioning friction in either piece—one action producing a change in the distance of the compensation-weight from the centre of motion, the other simultaneously taking the compensation-weight either backward or forward, to be so acted upon by the leverage of the first action, that the compensation-weight is taken over any space required for the perfect correction of irregularity arising from temperature; or, in other words, the compensation-weight is moved further down the lever by an increase of cold, and higher up by an increase of heat. In the ordinary compensation-pieces, the distance between the centre of gravity of the weight and the junction of the compensation-pieces is lengthened by decrease, and shortened by increase, of temperature; so that the compensation-weights are removed too far out from the centre of motion by cold, and not brought sufficiently inwards by heat. -Literary Gazette, No. 1328.

FRODSHAM'S CHRONOMETER COMPENSATION-BALANCE.

As a certain and effectual method of correcting the Compensationbalance in Chronometers, whereby they may be made to keep the same time both in the extremes and middle temperatures, Mr. Frodsham has exhibited to the British Association, a diagram of the ordinary balance, with the mean-time screws placed on one side of the bar of the balance. In the centre of this bar, on the exterior rim, was screwed a short piece of steel, extending along the outer rim three or four degrees, but perfectly free. In this piece were several small holes to receive a screw, when the balance was corrected by the ordinary compensation-pieces; that if the chronometer kept the same time at 55° or at 90°, it would lose considerably at 32°; the screw in the steel piece was, therefore, to be placed in such a hole, being just in contact with the outside of the rim of the balance: when at 55°, that would reduce the length of the acting part of the compensation; and, in the colder temperatures, would allow it to recede only that distance from the centre of the balance which would make the chronometer keep the same time as in the higher and middle temperatures. One great advantage of this invention was stated to be, that it may be applied to the balance of any chronometer which is now completed on the usual construction.-Literary Gazette, No. 1238.

STANDARD WEIGHTS AND MEASURES.

THE REV. Dr. Peacock, dean of Ely, has read to the British Association, the Report of the Commission on this important inquiry. The

author, after stating that the Imperial Standards of Weights and Measures, (the yard, the pound, the gallon, and several of their multiples,) had been lost in the fire which destroyed the two Houses of Parliament, mentioned, that a Commission of which he was a member, had been appointed to report on the best means of restoring these standards. The standard pound weight was Troy weight (5,780 grains,) though the pound avoirdupois (7,000 grains) was used throughout the country, in the proportion, perhaps, of 10,000 to one of Troy. The Commission recommended the standard pound to be the representative of the avoirdupois, and not, (as before,) of the Troy pound; that, hereafter, the use of the Troy pound should be abolished, except for a very limited number of transactions, and that the avoirdupois pound should be considered as the standard pound of Great Britain. They recommended that measures of capacity should be determined by measures of weight,-by far the most convenient method, inasmuch as weighing was a much more accurate operation, than, for instance, the formation of a perfect cube. The Commission also ventured to recommend strongly some alterations in the coinage, and the systems of weights and measures, arising out of a more extensive introduction of the decimal scale. The nearly unanimous determination of the Commission was, that any attempt to interfere materially with the primary units of the coinage, weights, and measures in ordinary use, would produce such confusion and bad consequences in the ordinary transactions of life, that they would adhere strictly to all those primary units, viz. the pound sterling of our coinage; the yard in the measure of length, (and also the foot, for there were two primary units in this measure ;) the acre, in the measure of areas; the gallon, in the measure of capacity; and the imperial pound, in the measure of weight..

As the coinage must necessarily be the basis of any changes leading to the more extended adoption of a decimal scale,-Taking the pound sterling as the primary unit, they proposed to introduce a coin of the value of 28. (one-tenth of the pound ;) another, either silver or copper, of one-tenth of 2s. (or 2d. and a fraction) which might be called a cent (the hundredth of a pound) and the thousandth part of the pound sterling, or nearly the value of our farthing, (of which there are 960 in the pound,) which new coin it was proposed to call a millit, (from thousandth.) The difference in the value of the copper coinage was less important, as it was merely a representative coinage, and had not an approximating intrinsic value, like the gold and silver coinage. For the proposed coin of 2s. various names had been suggested-as Victorine, rupee, and florin; it being not much different from the value of some of the rupees of the East Indies, or the florin of the Continent. Under this new decimal scale, the shilling would be retained, and also the sixpence, but the latter under another name, more representative of its value. For the half-crown would be substituted the 2s. or Victorine. The author next dwelt at some length on the advantages of this change, in the extensive money transactions and accounts of bankers and merchants: in the establishment of the Bank of England, for