Fig. 1 is the external cylinder, closed at bottom, and sunk perpendicularly into the ground, with its margin on a level with the earthy surface. Fig. 2 is the inner cylinder or rain-gauge, open at top, to act as a funnel for receiving the rain, but closed at the bottom, except the central stop-cock, fig. 3, for letting off the water. This inner cylinder or gauge, is no narrower than its case, unless in so far as to allow of its being easily lifted out for the purposes of adjustment. This inner cylinder is furnished with a shoulder or flange, fig. 4, to close upon the mouth of the case, and prevent the entrance of any earth, sand, or leaves, so as to obstruct the easy elevation of the gauge. Fig. 5 is the surface of the grass plot in which the gauge is placed, and which must be kept in a trim condition in its immediate neighbourhood. Fig. 6 is the hollow float to which the index-rod 7 is attached. The rain which falls into the mouth of the cylinder will be conducted by the funnel, fig. 8, situate an inch and a half within the margin (to which it is soldered) into the receiver, fig. 2, and raise the float to a corresponding degree. Fig. 9 is a thin vertical strip extending across the middle of the mouth, with a sheath at the centre to embrace the rod, as a guide, and to serve as determining the zero of the scale and the indications of change. When the stopcock, fig. 3, has been open, and the water let off, the beginning of the scale on fig. 10 will usually be a little lower than the marking edge, fig. 9. In this case, a little water is poured into the cylinder, in order to bring the commencement of the scale to zero, or fig. 10, and, on the falling of rain, the index rises, and, being divided into inches and tenths, numbered downwards on the rod, the quantity is readily seen by inspection. The position of the gauge in a well-trimmed grass plot, at a distance from houses, walls, or trees, seems to me to obviate all risk of any extra water getting in, as the points of the grass effectually prevent any such occurrence. Those observers, however, who are particularly fastidious on the subject, may adopt a brush to be placed around the margin of the gauge, as recommended by Mr Thomas Stevenson, civil engineer, in this Journal for July 1842. The size of the gauge, or the area requisite for receiving a fair amount of the falling rain, can scarcely be said to have attracted sufficient notice. If we assume that the acceleration of the current would take place, by passing from a grassy surface over the open space of the mouth of the gauge, and a corresponding derangement of the motion of the rain-drop, then it must follow, that the larger the area, the greater will be the amount of error from this source. In order to put this to the test, I placed in the same grass-plot with a Thom's gauge of seven inches in diameter, three other gauges of one, two, and three inches in diameter, and obtained the results for three months, viz. :— The grass-plot was not free from eddies, arising from buildings, trees, and walls; but as all the gauges were nearly similarly exposed, and as they gave nearly similar results, I am inclined to think, that a receiver of one inch in diameter is as trustworthy as one of seven inches. When the instrument is to be made of copper (the most suitable ingredient), the small size reduces the expense. I have noticed the index-rod as divided into inches and tenths. The eye, after a short practice, has little difficulty in halving or quartering the tenths; and this is a degree of accuracy as great as the circumstances of the case warrant us in aiming at. The inequality in the fall of rain, at two places within less than a mile of each other, forbid us to expect any very accurate correspondence among gauges, even at mo derate distances apart, although similar in form and position. The gauge exhibited to the Society, and which was three inches in diameter, and two feet in depth, was constructed for me by Mr James Bryson, Princes Street, Edinburgh, who has furnished several similar instruments, now in operation in different parts of the country. = In conclusion, I may add, that the average annual fall of rain at Aberdeen, according to six years' observations with Mr Thom's gauge, was 304 inches. According to Mr Thom, the average of thirty years at Rothesay, in Bute, was =48-29 inches. The maximum annual quantity =71.37 inches, fell in 1811, and the minimum quantity =38.45, in 1803. NEW COLLEGE, Edinburgh, June 18, 1849. New Adamantine Mineral from Brazil. M. Dufrenoy lately exhibited before the French Academy a specimen of a mineral from Brazil, which appears to be to the diamond what emery is to corundum, as stated by M. Elie de Beaumont. Among some specimens recently sent to the Ecole des Mines, by M. Hoffman, a dealer in minerals, were two which were stated to be hard enough to polish the diamond; and, in fact, the hardness of these specimens was found to be superior to that of the topaz. This substance was analysed by M. Rivot, mining-engineer, who had at his disposal one large fragment weighing 65.760 grs., and several small pieces, weighing rather less than 0.50 gr.; the latter only were analysed. The large fragment appeared to come from the same alluvial formation as that in which the Brazilian diamonds occur. Its edges are rounded by long friction; but it has not the appearance of a rolled flint. It is of a slightly brownish dull black colour. Viewed with a glass, it appears riddled with small cavities separating very small, irregular laminæ, which are slightly translucent and iridescent. The brown colour is very unequally distributed throughout the mass. On one of the faces the cavities are linear, which gives it a fibrous aspect similar to obsidian. It cuts glass readily, and scratches quartz and topaz ; its density is only 3.012. The small fragments subjected to analysis weighed, 0·444 gr., 0·410 gr, and 0.332 gr.; their densities were respectively 3·141, 3-416, and 3.255. These numbers indicate great difference in the porosity of the specimens; they lead, however, to the conclusion, that the density of the substance is very nearly the same as that of the diamond. By means of long calcination at a brightred heat in a covered crucible, the specimens were not altered; they retained their aspect, hardness, and weight; they do not, therefore, contain any substance volatilizable by calcination out of contact of the air. This result, certainly, does not prove the igneous origin of these diamonds, but renders improbable the idea expressed by M. Liebig, that diamonds are derived from the transformation of organic vegetable matter. The three specimens were successively burned in pure oxygen gas in the apparatus employed by M. Dumas for the combustion of the diamond. The oxygen obtained from chlorate of potash was contained in a gasometer; it was dried and purified before it reached the combustion tube, by passing through two tubes containing sulphuric acid and pumice, and one tube with potash; employing this method with the precautions indicated by M. Dumas, 100 of the first specimen gave, carbon 96.84, ash 2.03; loss 1·13: second specimen gave, carbon 99.73, ash 0.24; loss 0.03: third specimen gave, carbon 99.87, ash 0.27; loss 0.36. In the combustion of the first specimen, only one bulb-tube with potash was employed, so that a portion of the carbonic acid produced by the combustion was lost; but in the other two experiments, in which two bulb-tubes, containing potash, were used, the second increased in weight some centigrammes. The last two analyses prove perfectly that the specimens are composed entirely of carbon and ash. The ash was yellowish; and in the first specimen it had retained the form of the diamond. When examined by the microscope, the ash appeared to be composed of ferruginous alumina and small transparent crystals, the form of which could not be ascertained. (L'Institut, Mars 2, 1849; Philosophical Magazine, vol. xxxiv., 3d series, No. 230, May 1849, p. 397.) Notice of some Plants which have flowered recently in the Royal Botanic Garden. By J. H. BALFOUR, M.D., Professor of Botany in the University of Edinburgh. (With a Plate of the Quassia amara.) Communicated by the Author. QUASSIA AMARA, Linn. Spec. Plant. ed. Willd., tom. ii., p. 567. Linn. fil. Suppl., p. 235. Lamarck Illust., t. 434. Decandolle, Annales du Museum, xvii. 323; Prodromus I. 733. Ad. Jussieu, Mémoires du Museum, xii., tab. 27, No. 43. Hayne, Darstellung und Beschreibung der in der Arzneikunde gebrauchlichen Gewächse, ix. 14 (tab.). Curt. Bot. Mag., pl. 497. Lodd. Bot. Cab., pl. 172.- In the April number of this Journal a description was given of the Peduncle terminal, about 2 inches in length, dark crimson, covered with small, acute, dark-coloured, hairy bracts, the lower ones empty, upper ones bearing each a pedicellate flower. Pedicels about of an inch in length, as long as the bracts, which are recurved at the apex; a contraction occurs where the flower is attached to the pedicel. Peduncles, pedicels, and bracts have scattered hairs. Calyx dark crimson, bibracteolate at the base; limb divided into five small, rounded, ovate segments, which are toothed at the margin. Corolla bright crimson, contorto-imbricate in æstivation, when fully developed still retaining a twisted appearance. Petals 5, with scattered hairs outside, more or less imbricated, and often slightly rolled in at the margin, rather more than an inch in length, ovate-lanceolate, blunt at the apex, curved at the lower part, where, by their apposition, they form a sort of sac. Stamens 10, longer than the corolla; filaments about 1 inch in length, of a pink colour, each with a white, scale-like, curved, hairy appendage at its base; anthers versatile, dithecal, lobes separated at the base, introrse, with longitudinal dehiscence; pollen trigonous, with 3 points where the intine protrudes. Ovary consisting of 5 united but easily separable carpels, supported on a large discoid gynophore, the lower part of which is adherent to the calycine tube. The 5 styles which proceed from the carpels are twisted together, and become blended so as to form at the upper part a single style, ending in a lobed and discoid blunt stigma; ovule solitary in each carpel, suspended, anatropal; embryo exalbuminous. Fruit (not perfect in the plant in the garden, and described therefore from a dried specimen communicated by Dr Christison) consists of five drupes spreading out horizontally from the gynophore, occasionally one or more are abortive; each drupe when dried is surrounded by a keel, which is very prominent on the upper side; epicarp darkbrown, with projecting reticulated veins. Seed suspended from the inner angle of the drupe. Embryo exalbuminous, cotyledons fleshy, radicle superior. Explanation of the Drawing. The drawing (Plate III.) has been executed by Mr James M'Nab, the Superintendent of the Botanic Garden. 1. Flowering branch, with impari-pinnate leaf and winged petiole. |