One is sent from Bombay, the other from Bengal ; and they differ from each other more in their external appearance than in their chemical composition. The extract from Bombay is of an uniform texture, and of a red brown tint, its specific gravity being generally about 1.39. The extract from Bengal is more friable, and less consistent; its colour is like that of chocolate externally, but, when broken, its fracture presents streaks of chocolate and of red-brown. Its specific gravity is about 1.28. Their tastes are precisely similar, being astringent, but leaving in the mouth a sensation of sweetness. They do not deliquesce, or apparently change, by exposure to the air.'

The strongest infusions and decoctions of the two different kinds of catechu, do not sensibly differ in their nature, or in their composition. Their colour is deep red-brown, and they communicate this tinge to paper; they slightly redden litmus paper; their taste is highly astringent, and they have no perceptible smell.'

The same plan was adopted in analysing the catechu, that was followed in the examination of the other species of astringent substances. Two hundred grains of powdered Bombay catechu afforded

Residual matter; chiefly sand and calcareous earth

Grains.

109

68

13

ΤΟ

The powder of the Bengal catechu gave, by similar methods of

analysis, in 200 grains,

Tannin

Peculiar extractive matter

Mucilage

Grains.

97

73

16

Residual matter; sand, with a small quantity of calcareous

and aluminous earths

14

• Of two pieces of calf skin which weighed, when dry, 132 grains each, and which had been prepared for tanning, one was immersed in a large quantity of the infusion of catechu from Bengal, and the other in an equal portion of the infusion of that from Bombay. In less than a month they were found converted into leather. When freed from moisture, by long exposure in the sunshine, they were weighed. The first piece had gained about 34 grains; and the second piece 354 grains. The leather was of a much deeper colour than that tanned with galls, and on the upper surface was red-brown. It was not acted on by hot or cold water; and its apparent strength was the same as that of similar leather tanned in the usual manner.'

The 4th Section consists of Experiments and Observations on the astringent Infusions of Barks, and other vegetable Productions. Two hundred grains of the strongest infusions of the barks of oak, Leicester willow, and Spanish chesnut, were submitted to evaporation; and in this process the infusion of the oak

bark

bark furnished 17 grains of solid matter; that of the Leicester willow about 161 grains; and that of the Spanish chesnut nearly an equal quantity. The tannin given by these solid matters was, in that from the oak bark infusion 14 grains; in that from the willow bark infusion 14 grains; and in that from the Spanish chesnut bark infusion 13 grains.' Calculating from the results of other experiments, the author is disposed to conclude that the compound of tannin and gelatine, from the strongest infusion of oak bark, consists in 100 parts of 59 parts of gelatine and 41 of tannin; that from the infusion of Leicester willow bark, of 57 parts of gelatine and 43 of tannin; and that from the infusion of Spanish chesnut bark, of 61 parts of gelatine and 39 of tannin.'

Two pieces of calf-skin, which weighed when dry 120 grains each, were tanned; one in the strongest infusion of Leicester willow bark, and the other in the strongest infusion of oak baik. The process was completed, in both instances, in less than a fortnight; when the weight of the leather formed by the tannin of the Leicester willow bark was found equal to 161 grains; and that of the leather formed by the infusion of oak bark was equal to 164 grains.'

When the process of tanning, however, was more slowly conducted, and was effected by weaker solutions, the increase of weight was much less, and the colour of the leather was deeper.

With regard to the relative quantities of tannin in different entire barks, the results were as follow: In the quantity of an ounce of its bark, the oak produced 61 grains of matter dissolved by water, of which 29 grains were taunin; the Spanish chesnut, 53 grains, of which 21 were tannin; and the Leicester willow, 71 grains, of which 33 were tannin. An ounce of the bark of the elm furnished 13 grains of tannin, and of the commou willow 11 grains; the same quantity of Souchong tea afforded 48 grains, and of green tea, 41 grains; 165 grains of matter soJuble in water, of which 78 grains were tannin, and 156 grains, of which 79 were tannin, were afforded, the former from an ounce of Sicilian, the latter from an ounce of Malaga sumach. Very little tannin was observed in cinchona or other febrifuge barks, and none in any of the strongly bitter vegetable infusions which Mr. Davy examined: but he has found it in sloes, port wine, and substances which contain sugar and vegetable acids; and he suspects that it exists in all matters possessed of the astringent taste.

The 5th and last Section is occupied with general observations relating to the subject of this paper. Though tanning may be quickly effected by means of strong infusions of barks of catechu, yet the author is of opinion that the leather, which

1

isced by a slower process, is stronger and softer; and the tins circumstance probably arises from a greater quantity of the extractive matter combining with the skin than could otherwise be the case. The different qualities of the leather, seem to him to depend very much, on the various quantities of this extractive matter, which have entered into chemical combination with it.

Catechu is the substance which, according to Mr. Davy's experiments, affords the greatest quantity of tannin; and it appears to him that if, according to the usual estimation, from four to five pounds of common oak bark are required to produce one pound of leather, about half a pound of catechu would answer the same purpose. He also concludes that, allowing for the difference in the composition of the various kinds of leather, one pound of catechu, for the common uses of the tanner, would be nearly equal in value to 2 pounds of galls, to 7 pounds of the bark of the Leicester willow, to pounds of the bark of the Spanish chesnut, to 18 pounds of the bark of the elm, to 21 pounds of the bark of the common willow, and to 3 pounds of sumach.'

Appendix to Mr. Wm. Henry's Paper, on the Quantity of Gases absorbed by Water, at different Temperatures, and under different Pressures.-The author here informs us that he has found, since the printing of his former communication, that the numbers assigned in it, as indicating the quanties taken up by water, of some of the more absorbable, and of all the less absorbable gases, are rather below the truth.' He communicates the results of his latest experiments, and farther explains the ideas suggested to him by Mr. Dalton on the absorption of carbonic acid gas by water, by stating that the absorption of gases by water is purely a mechanical effect, and that its amount is exactly proportional to the density of the gas, considered abstractedly from any other gas with which it may accidentally be mixed-hence, if the residuary gas contain, or any other proportion, of foreign gas, the quantity absorbed by water will be, T, &c. short of the maximum.'

The usual Meteorological Journal terminates this part of the present volume. Part II. has just made its appearance.

ART.

ART. VIII. A Chronological History of the Discoveries in the Sch Sea, or Pacific Ocean. Part I. commencing with an Account f the earliest Discovery of that Sea by Europeans, and terminating with the Voyage of Sir Francis Drake, in 1579. Illustrated with Charts. By James Burney, Captain in the Royal Navy. 4to. PP. 4c0. 11. 4s. Boards. Nicol, &c. 1803.

MA

ARITIME discovery possesses most of the qualities which excite and gratify the curiosity of civilized man; and though we may not always be able to approve the motives which have prompted nations and individuals to explore un known seas, we are soon induced to forego this preliminary objection, in contemplating the beneficial consequences which have resulted from their enterprize. Commerce, which has polished the world by a gradual communication of enlightened legislation, and of all the comforts of life, has also received its greatest extension from this spirit; to which we, as Britons, are eminently indebted for those important parts of the strength of the empire, our navy, colonies, and distant dominions. We therefore enter with great pleasure on the review of a work which is intended to trace discovery regularly from its source; and which proceeds from the pen of one whose profession, and whose personal experience as a companion of the immortal Cook, so well qualify him for the office which he has assumed.

From a prefatory address to Sir Joseph Banks, we learn that this volume is to be considered in two points of view; as an intended specimen of the possibility of a general digest of Maritime Geographical Discovery, and in its own individual character. The author observes that the accounts of voyages now in the possession of the public, are alone sufficient, both in number and in quantity, to form a considerable library. The length to which some of the relations have been extended, especially those of a modern date, and the want of any general arrangement, are become vexatious obstructions to the acquisition of knowledge in maritime geography.' To obviate these evils, he proposes, 1st. a classified digest of such voyages as baye afforded real information; and, 2dly, compression. In considering the former of these requisites, he points out the objections to a chronological or national arrangement in a general history of voyages; and principally because either of these arrangements would be attended with this great inconvenience, that to obtain a satisfactory account of any one subject, it might be requisite to consult every volume in the collection, however extensive.' He therefore bestows a decided preference on the method of classing voyages according to some hydrographical division of the globe, preserving to each division the

chronological order of narration. It is necessary to give the proposed classification, in order that our readers may comprehend the full scope and intention of Captain Burney's plan, and thence be enabled more distinctly to appreciate its merits:

• The following division is proposed as one which appears capable of preserving its classes in a great measure distinct from each

other.

The first class may contain the voyages to the north of Europe; those in the north seas, and towards the north pole.

The second, those along the west coast of Africa to the Cape of Good Hope; and the discoveries of the Atlantic islands.

The third, east from the Cape of Good Hope to China, including the Eastern Archipelagos between New Holland and the coast of China. Japan might have a section to itself as a supplement to this

class.

The fourth might contain the whole of the discovery of the east side of America, except the Strait of Magalhanes and of Le Maire, which are more connected with the voyages to the South Sea.

The fifth class may comprehend the circumnavigations and voyages to the South Sea. With these, the discoveries on the west coast of North America are so much interwoven, that they cannot, without disadvantage, be separated.

The discoveries made by the Russians in the seas near Kamtschatka, and from thence to the north, would appear not improperly as a supplement to the fifth class.

na

• New Holland might form a sixth class. This country would turally have divided itself between the third and fifth, had not its importance so much increased within the few last years, that it now requires a distinct class to itself.

The foregoing division is offered as a sketch for a general plan: the classes are capable of modification, according to the convenience or inclination of those who may undertake any part of the task.'

In treating of the other requisite, compression, the author particularly notices the superabundance of nautical remarks with which some accounts are loaded; even in known seas, and when far distant from land, as if it were a matter of importance to settle the exact geography of a spot in the middle of the ocean, where no mark exists by which it can be ever recognized. To remedy this by striking out any part of what is useful, is to exchange superfluity for defect. Many have sup posed that to abridge is a work of no labour; that to read and reject such parts as are disapproved, is nearly the whole that is required: the consequence has been, that abridgments have been undertaken by persons very inadequately skilled in the subject of which their original consisted.' In a complete account of a voyage, Capt. B. remarks, every thing should be mentioned which possesses any prospect of utility, and the quantity of remark may be proportioned to the importance and to the. occasion;