TRANSACTIONS OF THE BRITISH ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE.

Report on Atmospheric Waves. By MR. BIRT.

The report consists of three parts:-the first having reference to the information we at present possess, relative to such individual waves as have been determined: the second treating of the barometric curves which result from the crossing of the north-westerly and south-westerly waves, the two principal systems common to Europe-the most prominent subject being that particular curve known as the "great symmetrical wave of November:" and the third embodying the results that have been obtained during the last year, illustrative of the symmetry of the "great wave," more particularly the locality of greatest symmetry, and the departure from symmetry in certain directions.

Under the second head, the author has thrown together the result of his inquiries into the forms presented by the barometric curves at certain stations, and has devoted attention to the symmetrical curve of November, as it has been observed at the Observatory at Greenwich, in the years 1841 to 1845. In connexion with this subject, the author remarked, "it has been assumed that the symmetrical wave of November consists of five subordinate waves, giving rise to the five maxima which characterize it, the central maximum forming the apex of the symmetrical curve, the remainder being subordinate thereto. (Association Reports, 1846, p. 125.)

"Upon a close inspection of the curves of the 'great wave,' as laid down from the Greenwich observations, six subordinate maxima can be traced, three on each side the central apex, which, in all the years, is by far the most prominent. The mean curve leads to the conclusion, that Greenwich is not the point of greatest symmetry, its closing portion being depressed more than two inches below the commencement. The next feature is the decided rise of the mercurial column, during a period of sixty-eight hours preceding the transit of the crest; the value of this rise is 7 inch, or about 010 inch per hour. The fall is not so precipitous; the barometer appears to be kept up in this locality by the first subordinate maximum succeeding the crest, so that, at the epoch of sixty-eight hours after transit, the value of the reading is more than two inches higher than at sixty-eight hours before transit. At eighty hours after transit a precipitous fall commences, which continues during the next twenty-four hours, the mercury sinking ⚫36 inch, or about 015 per hour. The fall afterwards continues, with two slight interruptions, answering to the subordinate maxima, until the close of the wave, 148 hours after transit."

The peculiar features of the mean curve, especially the difference between the initial and terminal readings, 241 inch, combined with certain features exhibited by the "great wave," at its last return, has suggested the possibility of expressing numerically the departure from symmetry for any station that may be selected. This departure from symmetry is strikingly manifested by the observations of 1846, especially as we proceed from Brussels, the European nodal point, towards VOL. XVI,-3RD. SERIES.-No 5.-NOVEMBER, 1848.

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Ireland and the north-west of Scotland, and is well seen in the series of curves, illustrating the author's report in the last volume of the Association Reports.

Three principal maxima characterize these curves on the 5th, the 9th, and the 12th of November; and the differences of altitude between those of the 5th and 12th, have been employed to indicate the deviation from symmetry in the direction already alluded to. The discussion of these differences, and the results deduced from them, form the third part of the report.

The author has laid down, on a map of the British Isles, these differences, and from them constructed a chart of the lines of equal deviation from symmetry-these lines range from 100 inch-which passes north-west of the Channel Islands, proceeds towards the Isle of Wight, skirts the shores of Sussex and Kent, and passes through Ramsgateto 550 inch, which passes through Limerick, is slightly curved as it crosses Ireland, and proceeds nearly in a straight line across the Scottish Islands, to the north-west of Great Britain. The values of these lines express the depression of the maximum of the 5th below that of the 12th. Among these lines, the author regards the direction of that representing 260 inch as the best determined. It appears to have passed near, and to the west of, Helstone, this station exhibiting a deviation of 258 inch; it then proceeded along the coasts of Cornwall and Devonshire, crossed the Bristol Channel, entered Wales, and continued its course across Glamorganshire, towards Brecon, which it left to the north-west, as it rather abruptly changed its direction, and proceeded towards Gloucester, which it passed through. It appears to have undergone considerable inflexion, as it traversed the central parts of England, rising again towards Nottingham, which is removed .025 inch from it to the west; it finally left the shores of England, at the south-eastern angle of Yorkshire, and entered on the Gerinan Ocean.

The author solicited attention to a feature which characterizes all these lines, especially the one just traced, viz., the decided inflexion they undergo as they pass over the land.

The chart exhibits two systems of inflexion, one being peculiar to Ireland and England; the general direction of the lines undergoing a change as the line of greatest symmetry is approached, the inflection being governed apparently by the masses of laud; and the other to Scotland, the inflexion being very decided over the land northward of the Firth of Forth.

From the single instance discussed by the author, the result appears to be, that the symmetry of the barometric curve is departed from in a greater degree at inland stations; a greater difference between the points selected, being exhibited at such stations than at the sea coast on either side. The report closed with some remarks on the non-persistency of the direction of these lines of deviation from symmetry, and on the high probability that they revolve about the nodal point of the two principal systems of atmospheric waves, Brussels.

Lond. Athenæum, Aug. 1848.

On the Advantageous Use made of the Gaseous Escape of the Blast Furnaces of Ystalyfera. By MR. J. PAlmer Budd.

This communication drew attention to an economical application of the heated gases which are usually allowed to escape from the top of the iron furnaces. It appears that the gases which are evolved from these furnaces, escape at a temperature which is about the melting point of brass. In the iron works at Ystalyfera, where the iron is smelted by the use of anthracite coal, advantage has been taken of this in a most ingenious manner. By an arrangement, which is in its character exceedingly simple, but somewhat difficult to describe without a model, (Mr. Budd's description was illustrated by a very nicely constructed one,) the hot gas is led off into another channel, by means of a strong current, generated through a chamber and air-way, from a point just below the top of the iron furnace. It is conducted, very little heat being lost in the passage, under the boiler of a steam engine; and it is found to be at a sufficiently high temperature to heat the boiler, without the consumption of any fuel whatever. Hence an immense saving is effected. Although only one furnace, and one boiler, has hitherto been adapted to this purpose, it is found to effect a saving of £350 a year. We may consequently expect that, when the experiment is further extended, and more of the furnaces so arranged that this heat may be economized, and employed for the numerous useful purposes to which it is applicable in a large establishment, the saving will amount to many thousands annually. This communication is to be printed entire in the Transactions.

Ibid.

On a Self-Registering Thermometer, with Twelve Months' Tracings of its Work. By M. HARRISON.

The principle on which the instrument acts, is the difference in the expansion and contraction of two metals, from the effects of heat and cold, and acting by the direct pull of the contracting metal, when it is kept in a straight line. It is made sufficiently powerful to overcome any resistance which the fulcrums of the levers, or the tracing pencil, may cause. I have selected cast iron and hard-rolled copper as the best suited for the purpose. I find, from tables published by Smeaton and others, that copper expands of its length, while cast iron only expands, with a variation of 180 degrees of Fahrenheit's thermometer, which leaves a difference of about the 12 of its length; and as the range of the thermometer in the shade, in this climate, is about 90 degrees, or half of 180, I have the part of the length of the copper bar employed as a moving power. I fixed upon a bar ten feet long, as being a convenient length; the two metals will then vary nearly the one-and-twentieth part of an inch, between the hottest day in summer, and the coldest day in winter. This variation I multiply by means of a compound lever, so as to get a sufficient scale to divide. The end of the last lever carries a pencil, which traces upon a revolving cylinder the variations that take place. In order to divide the scale

accurately, I procured a standard thermometer, by Messrs. Troughton & Simms. I placed it in the same situation, and made several observations in the day, for some weeks, in the spring of the year, when the range of the thermometer is the greatest. After I had got the scale properly divided, I engraved it on a plate of copper, in order to get a number of copies printed. The only attendance the instrument now requires, is to put a fresh paper upon the cylinder, by means of stretching screws fixed on one side of the cylinder, once a week, when I wind the time-piece up.

A, copper bar, one inch in diameter, and ten feet long; B, cast iron trough, to which the copper bar is made fast at the bottom; C, brass cap. soldered fast to the copper bar, with knife edges on the under side, which rest on the tubular end of the first lever D, its fulcrum rests on the upper end of the cast iron trough B; E, flanges to bolt the trough to the outer side of a wall, near the angle of a room; F, part of the cast iron trough which passes through the wall into the room, carrying the fulcrum of the second lever I, and to which the revolving cylinder G is fixed; H, a weight to keep the first lever D steady on its bearings, and to counterpoise the second lever I; K, tracing pencil; L, a screw working in the edge of the wheel M, and coupled to the minute hand of the time-piece, making one revolution in an hour; the wheel M is fixed to the axis of the cylinder, and has 192 threads cut in its edge, and would make one revolution in eight days; N, a binding screw, to adjust the pencil to the proper hour line, when a fresh paper is put on

once a week; O, brass rings, made fast to the cast iron trough, to keep the copper bar steady, but through which it can move; the dotted line shows the side of the iron trough.

The instrument acts by the difference in the expansion of copper and iron, that difference being multiplied about 120 times, by a compound lever. The scale was obtained by placing in the same situation a standard thermometer, by Messrs. Troughton & Simms, for several weeks, in the spring of the year, when the range is the greatest, and making a great number of observations each day.

Tabulated results for the year 1847, taken from tracings by the Instrument described.

Prof. Lloyd observed, that he much feared, as the indications of this thermometer were derived from the unequal expansion of different metals, magnified by a system of levers, that the bearings of the levers would be found not to move continuously, but by starts.

Sir W. S. Harris thought it likely some correction would be required for the hygrometrical state of the paper on which the curves were traced, as well as for the effects of changes of temperature of other parts of the instrument.

Prof. Lloyd, having been requested, by several members, to describe a barometer on a new principle which he had lately seen, said that it was a French invention. A cylinder of copper, with a very thin and corrugated end, was partially exhausted and hermetically sealed; and the effect of the varying pressure of the atmosphere, on the thin end, was magnified by a system of levers, so as to affect the index of a dial, very little larger than a watch dial. A friend of his had tested the indications of the instrument, by placing it under the receiver of an air pump, and observing its march, in comparison with the indications of the long gange, and found them to agree to less than the 1-100th of an inch. Mr. Jenkins mentioned some remarkable cases of the discrepancy of the indications of a number of compared thermometers, ranged along a wall at short distances, and at intervals of a quarter of an hour.

Ibid.

On some New Relations of the Diamagnetic Force. By PROF. PLÜCKER. Mr. Plücker gave a short account of experiments belonging to a new magnetic action. A crystal with one optical axis, being brought between the two poles of a magnet, there will be a repulsive force, going out from each of the poles, and acting upon the optical axis. According to this action, the crystal, if suspended, will take such a position, that its optical axis is placed within the equatorial plane. When the