of the mode of formation of the tube which Mr. Smith has first pointed out. The tube he has found to be completely external, and formed by a deep longitudinal depression in the surface of the pulp, which is destined to become the tooth. When the pulp is converted into tooth, the edges of it come gradually into contact, and thus convert the depression into a tube. This tube is not lined with enamel, and in the common viper to the two sides of the tooth are cemented together by the enamel, which thus constitute the sutor of the tooth.

XII. On the Parallax of a Aquila. By John Pond, Esq. F.R.S. Astronomer Royal.-From a set of observations made with the telescope, erected for the express purpose of observing this star, in which it was compared with 7 Pegasi, Mr. Pond considers himself entitled to conclude, that it exhibits no evidence whatever of having a parallax.

XIII. On the Parallax of the fixed Stars in right Ascension. By John Pond, Esq. F.R.S. Astronomer Royal.-The observa tions contained in this paper coincide with those formerly made by Mr. Pond, in showing that the parallax of the brightest stars cannot possibly exceed half a second, and that it is very unlikely that it should amount to half that quantity.

XIV. An Abstract of the Results deduced from the Measurement of an Arc of the Meridian, extending from Lat. 8° 9′ 38.4" to Lat. 18° 3′ 23.6" N. being an Amplitude 9° 53′ 45.2′′. By Lieut.-Col. William Lambton, F.R.S. 33d regiment of foot.Some account of the results of this interesting measurement was given in the last number of the Annals of Philosophy. Col. Lambton is in hopes that the measurement of the arc will be continued still further north, and that at some future period it may be extended even as far north as Delhi.

ARTICLE VIII.

Proceedings of Philosophical Societies.

ROYAL SOCIETY.

Feb. 25.-A paper, by Sir H. Davy, was read, on the formation of mists in particular situations. The author commenced by observing, that the fall of temperature after sun-set is greater on land than on water; and referred to the well-known peculiarity in the expansibility of water at temperatures below 40°, as the cause by which both the water and the superincumbent air are preserved at a superior temperature. When, therefore, according to Sir H. Davy, the cold and comparatively dry land air mixes with the warmer and moister air resting upon the water, the diminution of the temperature of the latter occasioned by this mixture has a tendency to separate a portion of its moisture in the form of mist.

At this meeting also, a paper, by Capt. E. Sabine, was read, entitled "Observations on the Dip and Variation of the Magnetic Needle, and on the Intensity of the Magnetic Force, made during the late Voyage in Search of a North-West Passage." The author stated, that the dipping needle employed in these observations was similar to that described by Mr. Cavendish, and made by the same artist. It was so adjusted, that on reversing the poles, the dip remained unaltered; and it was placed in the direction of the magnetic meridian by a compass, placed at such a distance as to remain during the observation for the purpose of occasional verification.

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In determining the intensity of the magnetic force, a magnet was employed to draw the needle to a horizontal position. The magnet was then removed at an observed moment, and the needle permitted to oscillate till the arcs became too small to be observed. At every tenth vibration both the arc and time were noted.

The azimuth compasses employed by Capt. Sabine to determine the magnetic variation, were made upon Capt. Kater's improved plan. The observations were generally made upon the ice, to avoid the great irregularities produced on board by the iron of the ship. The results of the whole of these different classes of observations were arranged in the form of tables.

March 4. A paper, by Dr. Brewster, was read, on the action of crystallized surfaces upon light. Malus had remarked that the action exerted upon light by the first surface of iceland spar is independent of the position of its principal section; that its reflecting power extends beyond the limits of the polarising forces of the crystal; and that as light is only polarised by penetrating the surface, the forces which produce extraordinary refraction begin to act only at this limit. He also remarked, that the angle of incidence at which this spar polarises light by partial reflection is 5610; and that whatever be the angle included between the plane of incidence and the principal section of the crystal, the ray reflected by the first surface is always polarised in the same manner. After stating these observations of Malus, Dr. Brewster proceeded to observe, that his experiments upon the subject led him to draw different conclusions, and rather seemed to indicate that the polarising forces extend beyond the crystal. He also showed that the force of double refraction and polarisation originate from the surface of bodies, though its intensity depends upon the inclination of the surface to the axis of the crystal, and that the ordinary and extraordinary image may be extinguished at pleasure, and thus a doubly refracting crystal be converted into a singly refracting one. He also showed that the change in the angle of polarisation produced by the interior force depends on the inclination of the reflecting surface to the axis of the crystal and upon the azimuthal angle

which the plane of reflection forms with the principal section gle

that the change in the direction of the polarisation depends

upon the angle which the incident ray forms with the axis of the crystal. The paper contained numerous experimental details.

At this meeting there was also read a paper, by Sir E, Home, giving an account of the fossil skeleton of an animal, several parts of which have been already laid before the Society in three separate papers. The author, after referring to his former papers, proceeded to describe, in general terms, and principally with the view of correcting his previous account, a specimen recently found nearly in an entire state. The only parts wanting were some of the bones of the pelvis and the lower part of the sternum. A beautiful drawing of the animal of its natural size accompanied the paper, which rendered minute description unnecessary.

March 11.-A paper, by C. Bonnycastle, Esq. was read, entitled, "On the Pressures which sustain a heavy Body in Equilibrium when the Points of Support are more than three." The author, after some general remarks, observed, that this is a problem which has hitherto never been satisfactorily investigated, though its assistance is necessary in estimating the strength of bridges and materials in general, and in determining the deflection and curvature of elastic plates. The difficulties attending the investigation of this problem were referred by Mr. B. to the too great generality of the method of investigation hitherto employed, and which, for the most part, has consisted not in the direct solution of the equation, but in comparing it with another admitting of a more easy solution. The author, after some further remarks, observed, that there is no method purely mathematical by which the difficulty can be surmounted; and that when abstractedly considered it appears impossible to determine the pressures which a heavy body exerts when supported on four or more fulcra. By considering, however, the circumstances under which pressure is usually generated, we shall be enabled, the author continued, to discover the law of its distribution, and this law must always govern its proportional quantities and intensities. Mr. B. then proceeded to examine the subject in this point of view, and to explain the general law of the distribution of pressure on determinate fulcra in different instances. The paper concluded with an investigation of the case, when the number of points of support is infinite; or in other words, consists of a line or plane surface.

March 18.-A letter by Dr. Granville was read, the object of which was to correct a mistake in his paper in the last volume of the Transactions of the Royal Society, and which had been pointed out to him by Dr. Maton.

SOCIETY FOR THE ENCOURAGEMENT OF ARTS, MANUFACels sri TURES, AND COMMERCE.

last:

90

Society has voted the following rewards since February

Mr. Barraud's Double Violincello. This instrument possesses

a greater compass than the double bass, and can be performed upon with as much facility as the violincello; and as its tone is much less powerful than that of the double bass, it will be found a most desirable acquisition in chamber concerts. The Society awarded its gold Isis medal to Mr. Barraud for this invention.

Mr. G. Rhodes's Warp Drier.-The warp is wound upon a sort of reel in a spiral manner, leaving spaces between each coil for the air to enter and dry the warp: it will be found very useful to woollen weavers, as it enables them to dry their warps in the house instead of exposing them at full length along the highways,, &c. as usual. The Society voted its silver Isis medal and 10 guineas to Mr. Rhodes for this invention.

Mr. Donovan's British Cured Herrings.-Mr. Donovan having resided for a long time in Holland, and witnessed the methods used there in curing their celebrated herrings, was at the pains of repeatedly bringing over Dutch fishermen and curers to instruct the Highland fishermen in those processes, and has completely succeeded therein. The Society has awarded its premium of the gold medal, or 50 guineas, to Mr. Donovan for this laudable undertaking.

Mr. Thomas Taylor's Repeating Alarum.-This instrument has been found of great service in the Royal Observatory at Greenwich, in giving the astronomer timely warning of the passage of certain stars, &c. either by day or night, and thereby affording him opportunities of making observations which might otherwise be lost. The Society voted the sum of 15 guineas to Mr. Taylor for this invention.

Mr. Richard Green's Gauge, or Plough, for cutting Leather Straps, &c.-This instrument will be found useful to saddlers, bridle cutters, harness makers, &c. as it performs its work with great accuracy and expedition, and the edge of the knife is never injured by coming into contact with the cutting board. The Society awarded its silver Isis medal to Mr. Green for this invention.

H

Mr. William Feetham's Chimney Sweeping Apparatus. By the introduction of a door into the flue, as near the top of the chimney as convenient, with a pulley affixed to it, that part of the chimney below the door may be conveniently swept by means of a line and brush, with an iron ball in a swivel affixed thereto; and the part above the door may be cleaned by another brush attached to a flexible handle; and in most cases without the use of climbing boys. The Society adjudged its silver medal to Mr. Feetham for this invention.

Mr. Fayrer's Clock.-This is an improvement on the threewheeled clocks recommended by Dr. Franklin and Mr. Ferguson, by which they will go longer without winding up, and will continue in action whilst winding. The Society voted its silver Isis medal to Mr. Fayrer for this invention. ja da aj tusloviyes Mr. William Bullock's Screen Spring.-The object of this

s bubbs bas

invention is to do away the injury which the pillars of screens sustain from the rubbing of the springs in common use; it is also applicable to other useful purposes. The Society awarded its silver Isis medal and five guineas to Mr. Bullock for this invention.

ARTICLE IX.

SCIENTIFIC INTELLIGENCE, AND NOTICES OF SUBJECTS
CONNECTED WITH SCIENCE.

I. Carbonate of Morphia.

In the number of the Annals of Philosophy for February, page 155, I gave the analysis of carbonate of morphia by M. Choulant. The proportions in which the morphia and carbonic acid are united, according to that chemist, differ so much from the proportions in which morphia unites with other acids, according to the same person, that there must obviously be an error either in the one determination or the other.

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Sulphate of morphia is, according to Choulant, a compound of

Here 9 represents the weight of an atom of morphia. By the acetate, it weighs 7-791; by the tartrate, 7-178; and by the nitrate, its weight is 12-15; but by the carbonate, it weighs only 2-16.

I shall here state the method by means of which Choulant formed the carbonate of morphia in question, and his mode of analysis, to enable my readers to determine the degree of confidence which they may put in the results which he has given us.

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He put a drachm of pure crystallized morphia in four ounces of distilled water, and forced carbonic acid into the liquid by pressure till the morphia dissolved. A mixture of eight parts dry muriate of lime and six parts snow was then placed round the cylindrical glass vessel containing the liquid. The carbonate of morphia was precipitated in crystals, and obtained pure by throwing the whole upon a filter.

To analyze the salt thus formed, he put 100 gr, of it into a small retort connected with a Woulfe's bottle, containing barytes. water. By the application of a moderate heat, the carbonic acid separated, and threw down the barytes in the state of carbonate: 22 gr. of pure morphia remained in the retort. The carbonate of barytes formed weighed 130-8 gr. This he considers equivalent to 28 gr. of carbonic acid. In reality, it is equivalent to about 28.8 gr.

He dissolved another 100 gr. of carbonate of morph and added acetate of lead as long as carbonate of lea

ater.