elastic properties, thus affording an analogy to the influence of heat in promoting the ductility of metals.

The chief uses to which caoutchouc is applied in this country are, 1st, The rubbing out of black-lead marks, by which it is universally known, and from which its name of Indian rubber is derived. 2d, The formation, by means of turpentine or linseed oil, of a varnish for air-balloons. 3dly, It supplies the surgeon with flexible syringes, catheters, and bougies; and the chemist with flexible tubes to gassometers and other apparatus, And, lastly, Mr. Howison has shewn that cloth of all kinds may be made impenetrable to water by impregnating it with the fresh juice; and that boots, gloves, &c. made of cloth thus prepared, which may be join, ed without sewing, by only moistening the edges with the juice, are more durable and retain their shape better than those made of pure caoutchouc. If more of this juice could be obtained, there is no doubt that it might be applied to a great variety of valuable and im portant purposes.

There are, however, various other plants, from which the elas tic gum may be obtained in smaller quantities. Dr. Barton men, tions several in America; and Mr. Woodcock, of Islington, has found it in some of the esclipias genus, aspecially a vincetoxicum, and a fruticosa*,

[EDITOR,

There is a curious mineral substance called mineral caoutchouc found in the spar mine, near Castleton in Derbyshire, and which bears in many of its properties a resemblance to the vegetable caoutchouc described above. It was thought, says F. St. Fond, an astonishing circumstance, that a substance which distils from exotic trees, which grow in the torrid zone, should be found between strata of argillaceous schist in the bosom of the mountains in the northern part of England. The depth at which this mineral has been found is not less than four hundred and fifty feet below the upper stratum. There appear to be two species of it, the elastic or compressible, and the solid or brittle; and several varieties of each. See Maw's Mineralogy of Derbyshire and the memoir of Faujas-Saint-Fond, in Phil. Mag, vol. xv, 225,

SECTION X.

Teak.tree.

Tectonia grandis.-RoxB.

THIS valuable timber tree, the glory of India, rises very tall, with a vast trunk, and is the only Indian wood which the termes fatule, or white ant*, will not touch.

The teak is the oak of the Eastern world, indigenous in Pegu, Hindostan, Malaga, and most of the oriental countries; and, like the oak in Europe, employed very generally for ship-building, and all inland purposes, when a strong and durable wood is required. From the excellent properties of this timber, and the peculiar soil and climate which it demands, the patriotic Society of Arts, Com. merce, and Manufactures have lately expressed their opinion, that it may be successfully cultivated in our West Indian and African settlements, and have consequently recommended a trial to that effect.

The best account of the teak-tree that we have yet met with is the following of Dr. Roxburgh, of Calcutta, whose botanical activity is well known to every one. We extract it from the Trans. actions of the Society of Arts, &c.

"The timber of the teak-tree is in India what the oak is in Eng. land: it is, however, unnecessary to enlarge on their comparative value, because oak will not grow in India. Our attention ought therefore to be confined to teak alone; not only as being by far the best wood we yet know of in this country for ship.building, but also for the house carpenter, and almost every other work where strong, durable, easily-wrought, light wood is required. The advantages to be derived from the cultivation of so valuable a tree, where nature has not bestowed it, must therefore be obvious to every one; particularly in Bengal, where it grows well, and the demand is so great. The teak-tree is a native of Pegu.

"Government, sensible of what is here stated, have long given every possible encouragement for an extensive propagation. But to render it still more general, the native land holders must

* See the ensuing book, for the singular properties of this insect.

be made sensible of the advantage they may expect to derive from large plantations thereof.

"The growth of the tree is rapid, and at all ages the wood (from various experiments) appears excellent. Some trees in the Honourable Company's Botanic Garden, brought from the Rajah. mundry Circar, in 1787, were, in 1804, from three to upwards of four feet in girth, at three and a half feet above ground, and high in proportion. These plants were about twelve months old when sent from the coast, so that their present age is about seventeen years. A tree promising so much advantage, in so short a space, compared to what the oak requires in England to become service. able in the marine yard, makes it highly worthy of every attention and encouragement. A few observations on rearing the plants from the seed seem necessary, as I have often known seeds from the same tree succeed with one person, and totally fail with another.

"The nut in which the seeds are lodged is exceeding hard, contains four cells, and in each is lodged a single small seed. It has been ascertained, that they perfectly retain their vegetating power in the growth, even as far as eighteen months; however, it is advisable to sow them about the beginning of the first periodical rains, or north-westers, after they are taken ripe from the tree in October. If sown about this period, or rather before than after, in well-shaded beds, about an inch asunder, and covered with about a quarter of an inch of earth, with a little rotten straw or grass spread over the earth, to keep the beds in an uniform state of humidity, by gentle waterings, should the weather prove dry; most of the nuts will be found to produce from one to four plants, in from four to eight weeks. However, it sometimes happens, that many will remain in the ground until the commencement of the second rains, nay even of the third; however this is rare, yet it will be advisable to sow the seed on a spot that can be spared, at least until the rains of the second season are well advanced; by not attending to this circumstance, many have thought the seed bad, consequently caused the ground to be dug up for other pur

poses.

"The plants, when they first make their appearance, are very small, scarce so large as a cabbage plant when it first springs from the earth; their growth is, however, rapid. When they are about

one or two inches high, they ought to be transplanted into other beds, at the distance of about six inches from each other, there to remain until the beginning of the next year's rains, when they are to be planted out to where they are to remain ; or they may, when from two to four inches high, be planted out at once to where they are to grow; and it is not perfectly clear but by so doing they succeed better; as in taking up plants of any considerable size, say from one to two or more feet high, the roots are very apt to be injured, particularly the sap root, which retards their growth much, nay often kills them.

"About Calcutta they thrive luxuriantly in most places where they have been tried, and any tolerable degree of care taken of them; so that the only observations which seem necessary to be made on this head, are to avoid sowing the seed, or planting in such places as are low, or subject to be inundated; to keep them clear from weeds, and sparingly watered during dry weather, for the first year only. In a good soil, not much overrun with that coarse white-flowered grass, called by the natives woola (saccha rum), they will scarce require any care whatever, after the first six months, from the time of being planted out where they are to stand. They will then be about eighteen months old, supposing them to have been transplanted twice, and in that time they will, in general, be from five to ten feet high, according as the soil is favourable, and out of all danger, except from north-westers.

"With respect to the distance at which plants ought to stand in plantations, every one's judgment can direct. The oak requires a great space, as the crooked parts thereof are the most valuable, and required for the knees and other curved timber in ship-building; but teak is naturally a straight-grained tree, and only used in Bengal, or at least in general, for the straight work; sissoo being commonly employed for knees, and other crooked timber; hence it may be concluded, that the straighter the teak trees grow, the more eligible for every purpose for which this timber is gene. rally employed in Bengal. They do not, therefore, require to be planted at a great distance; suppose from six to ten feet, in quin. cunx order; by being so close they grow straighter, and protect one another while young, which is particularly wanted where violent gusts of wind, such as our north-westers, prevail. When the trees grow up, they can be thinned out to advantage, as the

The

timber of the young trees will answer for a variety of uses. seed of this tree we have now in such abundance as to render a few hundred plants, in the hundred biggahs, of little or no importance; and if the ground on which they are planted is not of the best sort, the more necessity there is for planting close."

[Pantolog. Roxburgh. Trans. Arts, Commerce, &c.

SECTION XI.

Tobacco.

Nicotiana Tabacum.-LINN.

THIS well known plant was first imported into Europe about the middle of the sixteenth century, by Hernandez de Toledo, who sent it to Spain and Portugal, at which time M. Nicot was residing at the court of Lisbon, as ambassador from Francis II.; in consequence of which he carried the tobacco plant with him into France, in 1560, and presented it to Catharine de Medicis, as a production of the new world. From the name of the Ambassador

it was called Nicotiana. It appears from Lobel, that this plant was cultivated in Britain previous to the year 1570; and the introduction of the custom of smoking it in England is ascribed to Sir Walter Raleigh. The cultivation of tobacco is now common to various parts of the globe; and though prohibited by the laws of this country, still the manufacture of it forms no inconsiderable branch of commerce. The vulgar name of tobacco it has obtained from Tobaco, a province of Yucatan, in South America, where it was first discovered.

There are two varieties of that species of nicotiana which is cultivated for common use; and which are distinguished by the names of Oronokoe, and sweet-scented tobacco. They differ from each other in the figure of their leaves; those of the former being longer and narrower than the latter. They are tall herba. ceous plants, growing erect, with fine foliage, and raising with a strong stem from six to nine feet high. The stalk, near the root, is upward of an inch diameter, and surrounded with a kind of hairy or velvet clammy substance, of a yellowish-green colour. The leaves are rather of a deeper green, and grow alternately at the distance of two or three inches from each other. They are oblong, of a spear-shaped oval, and simple; the largest about