contains a great deal of flinty matter. The tree-which is called in Spanish El Caouto, or El Caouta; in French, Bois de Fer; in Brazil, Caraipe; and in English, pottery tree-is now known to botanists as the Moquilea utilis, H.f. Aublet was the first to bring the tree into notice, and it was at one time placed in the natural order Ternstromiaceæ, under the name of Caraipa angustifolia. Further information and research, however, has caused it to be placed where it now is. Sound and durable as the wood is, it is on the bark that the natives set the greatest value. The Indians employed in the manufacture of pottery from its bark always keep a stock of it in their huts for the purpose of drying or seasoning it, as it burns more freely, and the ashes are collected with greater ease than when it is fresh. For the manufacture of the pottery the ashes of the bark are powdered and mixed with clay, the purest clay that can be obtained from the beds of the rivers is preferred on account of its taking up a larger quantity of the bark ash, and producing a stronger kind of ware. The most valued bark, or that which contains the largest quantity of silex, is produced by trees which grow in a rich but dry soil. Those growing in low or sandy forests being much inferior in the quality of this deposit. In the best kinds the silex can readily be seen with the naked eye, but to test the quality of the various kinds of bark, the natives burn it and then try its strength between the fingers; if it breaks easily it is considered of little value, but if, on the contrary, it requires a pestle and mortar to break it, its quality is pronounced good. Though the proportions of ash and clay are varied at the will of the maker, and according to the quality of the bark, a superior kind of pottery is produced by mixing equal portions of fine clay and powdered ashes of the bark. All sorts of vessels of large or small size, for domestic or household use, are made of this kind of ware, as well as vases or ornamental articles, some of which are painted and glazed as in Fig. 6, which is a representation of a specimen in the Kew Museum. The figures upon this vase are not burnt in, but are merely superficial, the colour being laid on with a brush and secured by a coat of glaze. Fig. 5 is a representation of an unglazed pot, with lid, the figures of which are in relief. Articles made of this ware are very durable, and will bear almost any amount of heat; they are consequently much used by the natives for boiling eggs, heating milk, and, in short, for general culinary purposes.

Having shown the great value of this bark to the natives. for a purpose which, to say the least, is novel in the application of barks, we will endeavour to arrive at the cause of such an adaptation by a brief exposition of its component parts.

The bark seldom grows more than half an inch thick, and is covered with a skin or epidermis frequently covered with lichens. A superficial examination shows nothing out of the common; the fresh bark, however, cuts somewhat similar to a soft sandstone, but, when dry, it is very brittle and flint-like, and sometimes difficult to break. By biting a piece of the bark the presence of silex can be well ascertained, as it grates between the teeth like fine sand. If we examine a section under the microscope, we find all the cells of the different tissues or layers are more or less silicated, the silex forming in the cells while the bark is very young. In the inner bark the silex or flint is deposited in a very regular manner, as will be seen by Fig. 1. The flint, however, from the ash of a porous cell of the bark assumes a very different appearance, as shown in Fig. 2. Fig. 3 shows a porous cell macerated, and Fig. 4 is a flint skeleton from a similar cell. The bark of young trees and branches contain a much larger quantity of water than that of old trees; the proportion of water, however, are more equal in the old and young woods. From an analysis made of both the old and young barks, the old was found to give 30.8 per cent. of ash, and the young bark 23.30. Of the different layers of the old bark, the outer gave 17.15 per cent., the middle 37.65, and the inner 31. A larger percentage of ash was yielded by the bark of an old branch, which was found to give 77. In comparison to the bark the wood is relatively poor in silex, the duramen, or old wood of an old trunk, giving only 2.5 per cent., and the alburnum, or young wood, 2 per cent. only.

The wood, bark, ash, and various specimens of the manufactured pottery, may be seen in the Kew Museum.

MARE VAPORUM AND THE LUNAR CLEFTS-
OCCULTATIONS.

BY THE REV. T. W. WEBB, A.M., F.R.A.S.

WITH the object of comprehending in a continuous description the whole extent of the Lunar Apennines, our guides have carried us considerably beyond the 1st Meridian, and into the 2nd Quadrant of the Moon. They now bring us back towards the W. to complete the Quadrant with which they commenced, and introduce us to the Mare Vaporum (F in our map). This is a level surface, of a lighter tone than the other Maria, and possessing no very definite boundary, but lying in a general sense between the S.W. slope of the Apennines and the crater Agrippa (26). There would be little to make the region worthy of especial notice were it not that its S. part contains a full development of one of the most curious of the lunar features, the system of CLEFTS (or Rills). Fortunately for the telescopic observer, this district, while it lies in so central a position as to be very little affected by foreshortening, contains two of the largest and most obvious of these mysterious formations, "in which," say B. and M., "an attentive observation can recognize something more than their mere existence." Before we proceed, however, to describe them, it may be premised that there is a difficulty, not merely in comprehending their nature, but even in providing for them a suitable name. This arises from the fact that we are so little familiar with anything analogous to them on the surface of our own globe. It is true that features do exist, which, viewed at a corresponding distance, might have a somewhat similar aspect. We might refer to the transverse fractures of the Balkan range, and of some of the chains of Greece, the Barrancas of Mexico, or the marvellous cañons of the Colorado River (described in INT. OBS. iv. 309), which may, perhaps, exhibit as great a similarity to the clefts of our satellite as the terrestrial does to the lunar crater; and more could not in fairness be expected. But still, the fissures of our globe are too exceptional to constitute a system such as obtains on the moon, and consequently to have received any generally accepted name. Astronomers, therefore, are somewhat at a loss how to designate the lunar crack, if such it may be termed. Schr., the first discoverer of these objects, in 17-8, called them "canals," or "rills": the former term is obviously unsuitable to a dry surface, and has gone out of use; the latter has held its ground among the German observers, and very deservedly so, as far as their language is concerned, in which it signifies a small furrow, or

groove. Its adoption, however, by ourselves, though sanctioned by some great names, does not seem free from objection, on account of the existence of a similar, but by no means equivalent English word, the derivation of which, from the Latin, rivulus, and its meaning as given by Johnson, "a small brook, a little streamlet," refer unequivocally to the presence of water. It is, however, frequently easier to find a fault than to mend it; and in the present instance (furrow having been rejected, on high authority, as not sufficiently comprehensive), if the employment of the term cleft is suggested, it need only be looked upon as a provisional arrangement, till something more appropriate has been brought forward in its stead. It would indeed be a gain to selenography, if the whole subject of lunar terminology were to undergo a careful revision at the hands of those whose geological as well as astronomical acquirements would enable them to frame such a nomenclature as would command universal acceptance.

But, to proceed from the name, to the objects which it designates. The lunar clefts are characterized by B. and M. as very narrow and long depressions either in a straight or moderately curved direction; occasionally serpentine or hooked in form with very steep,* parallel sides, and usually without any external rampart: in Full Moon they appear as delicate white lines; near the terminator usually as black ones, as we perceive only the shaded interior. They sometimes pass through or close by small craters, or come to an end in them; at others they lie isolated in level surfaces, without any marked termination; in fact, one of their frequent characteristics is this want of apparent object, as we might speak with reference to the handywork of intelligent beings. They are frequently hemmed in by mountains, but do not appear to run straight over them; occasionally they are found to unite like veins, and even to intersect one another. Their individual breadth varies but little; if there is any enlargement, it is somewhere in the middle, never at the end [rather an inattentive assertion, by the way]. They occur in every kind of surface, excepting on lofty summits, or in the centre of the great plains; being of course less distinguishable towards the limb. A few of them are only from 9 to 14 miles in length; the generality 45 to 70; some, again, reach a maximum of 115 to 140 m.: their breadth is in places not inconsiderable, a mile or upwards; but they may be traced down to of that size.t Connecting links with other formations may often be perceived: the enlargements occasionally noticed take the form of longish craters, or if these are frequent, the whole cleft appears almost like a chain Schmidt considers them not extremely steep.

+Schmidt gives their depth from 100 yards to mile.

of minute craters, with a lateral communication throughout: on the other hand, there are regions where contiguous mountains form, with their straight and parallel sides, gorges much resembling these clefts, and where long straight valleys are dis ingnished from them chiefly by their greater proportional breadth and inferior steepness; and several valleys of this kind are to be met with in the immediate neighbourhood of true clefts, and parallel to them. From these and other indications, such as their want of connection with any definite object, their occasional repetition in parallel lines within a small distance, and more especially their magnitude (as Schr. had already perceived), the idea of an artificial origin must be aid aside.

On this subject B. and M. have some remarks, which, though referring to speculations which have never found great favour among ourselves, are still worthy of consideration. They observe that, but from inattention to the scale of the objects we are studying, and from the unreasonable expectations entertained at the end of the last century of a marvellous increase of magnifying power (some persons, in Germany we may presume, seem to have been anticipating the use of powers of 15,000!), the idea of these clefts being lines of road, or anything else of an artificial nature, would never have been seriously entertained.* In all such analogies, they judiciously remark, one very important point has been ignored-the relative proportion of gravity on the different bodies of the system. When this, as on the Moon, is 63 times inferior to that on the Earth, fresh relations are introduced between power, weight, and motion; and while we have no positive information as to artificial products on the Moon, it may be maintained with great probability that they would be totally unlike our own, and that, even if our optical means were capable of reaching them, they would not appear in any recognized or familiar form. Remarks of this kind are valuable if they check the vagaries of irrational fancy. We should take care, however, not to push them too far; it would be possible, though much less probable, to err in an opposite direction, and to impede the progress of discovery by an overweening estimate of our own previous conclusions.

The hypothesis of their being actually existing or dried-up water-courses may be disposed of with little trouble. All modern observers are agreed as to the absence of water, at least in any noticeable quantity, from the Moon as it now is; but could we conceive, with Gruithuisen, that it had formerly

Gruithuisen referred them partly to dried river-beds, or natural clefts, partly to artificial clearings through forest lands, used in either case as lines of communication.