circumference of eight feet; yet it has been found that this singular rapidity of growth by no means diminishes the density and durability of the timber, which has been already found to be equally adapted to the purposes of naval and domestic architecture. Granting that, for shipbuilding, this larch were inferior to the oak, this affords no solid objection to its use as a valuable addition to the resources of the State, as it attains perfection in one half of the period required for the oak attaining its full value. There is, however, reason to conclude, that the larch has been of late prematurely cut down.

The bark of the oak had hitherto been used almost exclusively in the process of tanning leather; but its daily increasing scarcity and consequent high price, arising from the great demand during the late war with the French, naturally led to the use of the barks of other trees, as substitutes for it. It was common to mix these last with oak bark, but in this way the result could never be accurately ascertained. It was necessary, therefore, to institute comparative experiments of the larch bark with the oak bark separately; and these, to avoid the ambiguity of trials on a small scale, were conducted by an eminent tanner, Mr P. Martin of Haddington.

(1.) Equal weights of skin were taken, as accurately as possible, from the same parts of the animal, and immersed, under the same temperature, that of the atmosphere in summer, in separate cold infusions of the same weight of the bark of the oak and larch, previously ground in the ordinary way, and treated in the same manner. Both sorts of leather were then dried: The same bulk of larch-tanned leather was found to be specifically heavier than that of the oak, but the proportional excess was not accurately ascertained.

(2.) In colour, the specimens sent to me, differed remarkably; the larch-tanned leather being of a light fawn, whilst that tanned by the oak bark was of a deep brown colour.

(3.) The larch-tanned leather absorbed water more readily than that of the oak, in these specimens. Circumstances of an accidental nature, however, sometimes regulate this property; such as more or less compression, by hammering, previous to the operations of the shoemaker; and it is well known that slow

drying tends much to regulate this property in leather of every kind. The best oak-tanned leather readily absorbs water when newly finished.

(4.) But, after all, the durability of leather is the great test of the utility of each substance used in this process; and, so far as respects this main object, the two sorts of leather, used as soles to each of a pair of shoes, were found to wear equally well. Were we to estimate a priori the relative value of the bark of Oak, Larch, and Leicester Willow, from the proportion of tannin afforded in the experiments of Sir H. Davy, the willow bark would excel that of the two others; but it seems probable that the inferiority of the Larch bark, in his experiments, arose from the trees being cut down in autumn;— a period when the sap, and its constituents of tannin and extractive, are greatly exhausted, from the previous formation of the young wood, in which they are easily detected; indeed, the proportion of extractive and tannin, in the succulent and newly condensed wood, is in some cases nearly treble the quantity existing in the old external layers of bark, especially in autumn; and from this it is probable that the annual prunings of trees, abounding with these constituents, might, with profit, be applied to the purposes of the tanner.

ART. XIV. Catalogue of the Right Ascension of Thirty-six principal Fixed Stars, deduced from Observations made in the Observatory at Konigsberg from 1814 to 1818. By WILLIAM BESSEL.

THE following important Catalogue of Stars was communi

cated by its eminent author to Baron de Zach, who has inserted it in his Correspondence Astronomique, from which it has been copied, and transmitted to us by one of the Baron's correspondents. M. Bessel has mentioned as a very remarkable circumstance, that the difference between the catalogues of Piazzi and Bradley, which he had found to be +2.489,* disappears

=

See Bessel's Fundament. Astron. p. 296, where he gives an account of this difference.

almost wholly, by taking the following fundamental catalogue as a basis.

Catalogue of the Right Ascension of Thirty-six Fixed Stars.

ART. XV.-Determination of the Longitudes and Latitudes of thirty-four places in the Mediterranean. By Mr CHARLES RUMKER. Communicated by the Author.

THE longitudes of the places contained in the following

Table, have been fixed by measuring, with the timekeeper, their meridional distance from La Valette on several short excursions which I made from that port, the longitude of which has been assumed at 14° 27′ 38.′′6, as determined by observations given in a preceding paper. (See p. 280.)

In those places where the latitude is not given, I had no opportunity of observing it with the sextant, the visible horizon being obstructed by land, and the sun's meridional altitude being too great for the artificial horizon. I then made use of the latitude taken from the chart in computing the hour-angle.

ART. XVI.-Account of a new species of Chronometer adapted to the eye-pieces of Telescopes, for reckoning fractional parts of a second in Astronomical Observations. Invented by M. BREGUET, Member of the Institute, and of the Board of Longitude of France.

M. BREGUET has been long known to the philosophers

of our own country as well as to foreigners, as one of the most distinguished artists which France has for a considerable time produced. His various inventions connected with Horology and Chronometry, indicate an ingenuity and a fertility of invention which are not often united in the same person, and such is the degree of excellence with which his timekeepers are constructed, that we may justly rank him with the Harrisons, the Arnolds, and the Earnshaws of our own country.

The ingenious instrument of which we propose at present to give a brief description, has been recently laid before the Board of Longitude of France; and though the commissioners have not yet given in their report, we have no doubt that it will be generally considered as promising to supply an important desideratum in practical astronomy. In ascertaining the disappearance of a star behind the wires of a transit instrument, we think there are few astronomers who would venture to say, that in ordinary circumstances they could observe to the fifth part of a second of time; but as this quantity corresponds to three seconds of right ascension, it becomes a matter of very high importance, in the present perfect state of astronomical instruments, to distinguish more minute portions of time.

The instrument by which M.M. Breguet propose to supply this defect, is shewn in Fig. 2. of Plate VII., where AB is a section of the eye-piece of a telescope through the diaphragm or field-bar placed in the anterior focus of the eye-glass next the eye; the black ring which it incloses representing the diaphragm itself: The box CD contains a chronometer, which, by means of the index G, points out every ten seconds upon the dial-plate EG, divided into ten minutes. Other two indices m, n, are made to revolve through the field of the telescope, and almost in the plane of the system of wires. The shortest of these n, marks