vulgaris, with some one or other of which it is often mixed.

It

is a mistake to suppose that the fresh leaves, when bruised, have the odour of mice; but this smell is instantly developed when they are rubbed in a mortar with liquor potassæ.

BRASSICACEE OR CRUCIFERA.-Sinapis nigra. As the plant is always cultivated for the sake of the seeds, it is unnecessary to describe it.

SILENACEE.-Saponaria officinalis. An extract is said to be still made of this plant, but it is never ordered by the regular professional man.

ROSACEA. - Potentilla tormentilla. Tormentil. Common on dry hilly pastures. The root-stock, which is the part employed, should be gathered by the herb collectors with the plant attached to it. It is a knob, about an inch and a half long, and an inch thick, irregular on its surface, dark brown externally, and internally flesh red. The leaves, which are sessile, consist of three oblong, acute, deeply serrated, somewhat hairy leaflets. The flowers are bright yellow, on slender hairy stalks, with the parts of the calyx and the corolla in fours.

Rosa centifolia. Damask Rose. This is always cultivated. The petals should be taken when the flower is half blown, and gathered in dry sunny weather. When they cannot be immediately distilled, they should be salted.

LEGUMINOSE.-Spartium, or Cystisus scoparium. Broom. Indigenous. The green tops are the parts employed. They are readily known by the angular, dark green, smooth stem, scattered over with small, ternate, stalked leaves, composed of obovate, obtuse, entire leaflets, silky in their young state. They should be used fresh, if they can be procured, for making the extract.

POLYGONACEA.-Rumex obtusifolius. Broad-leaved dock. Although not officinal, yet this the most common is one of the most active of the docks, and is occasionally ordered. The root is many headed, and internally yellow. The leaves are large, stalked, deep green, veiny, cordate, blunt at the apex, crenate and crisped on the margin. The flowers are in long clusters, composed of numerous many-flowered whorls, the lower ones distant and leafy; the root is the part employed.

Rumex acetosella. Sheep's sorrel. It is now scarcely or never used.

CAPRIFOLIACEE.-Sambucus nigra. Is now in flower the flowers are officinal, and are distinguished by being in large smooth cymes, cream coloured, and having a sweetish, heavy odour. They should be gathered in dry sunny weather, and distilled as soon as possible after they are gathered.

ASTERACEA.-Artemisia absinthium. Wormwood. Common on waste ground. This herb is known from the other indigenous species, by the close silky hoariness of the entire plant. The

leaves are alternate, doubly pinnatifid, with blunt entire segments, green on the upper disk. The lower leaves are on long footstalks, the upper on short broad and winged petioles. The twigs should be collected before the flowers run to seed. The flowers and upper twigs are odorous, aromatic, and bitter; the lower, or woody parts of the stem, are odorous and aromatic, but not bitter; the former, therefore, only should be collected. LABIATA.-Lavandula vera. Always cultivated.

Mentha viridis-Piperita-Pulegium are cultivated for medicinal use.

Marrubium vulgare. Common in hedge rows. The stem is quadrangular, leafy, covered with fine woolly hairs. The leaves are on longish stalks, wrinkled and veiny. The flowers are white, in dense whorls; the teeth of the calyx rigid, recurved, spreading, the five alternate teeth being smaller than the others. The whole herb is hoary, has an unpleasant aromatic flavour, and a very bitter taste.

SCROPHULARIACEA.-Digitalis purpurea. Foxglove is abundant on sandy and chalky soils, and in moist situations. Its leaves are alternate, ovato-oblong, crenate, veiny, downy and velvety to the touch, of a dull green colour, and tapering at the base into winged footstalks. They are from six to ten inches long, gradually diminishing in size from the bottom of the stem upwards. Foxglove is a biennial plant, and its leaves possess little activity in the first year of their growth, when they apparently rise from the root. The leaves should not be collected until the plant is fully in flower. They are sometimes adulterated or mixed with the leaves of Symphytum officinale, Comfrey, which, however, are easily distinguished by their wavy disk and rough edge; and also with those of Verbascum thapsus, Great Mullein, which are densely covered with white, branched, woolly hairs. In drying digitalis, the leaves should be freed from the mid-rib and footstalk.

SOLANACEA.Hyoscyamus Niger. Henbane is found on waste grounds. It is a biennial plant, and possesses little or no activity in the first year of its growth; but the leaves may be collected at any time before the plant seeds, or, indeed at any time in the second year. The leaves are sessile, clasping, decurrent, oblong, acute, unequally slashed, pale dull green, covered with long glandular hairs, which make them feel soft and clammy. The flowers are axillary, among the floral leaves, of a funnelshape, the corolla of a dingy yellow, beautifully reticulated with purple veins. The whole herb has a peculiar unpleasant odour. The leaves should be quickly dried, and never kept longer than one year.

Atropa Belladonna.

Dwale, deadly nightshade, is found in waste places. The root is perennial, the plant annual. It is

now in flower, and in the best state for medicinal use. No plant is so easily recognised by its botanical characters, yet other plants are often substituted for it, by the herb collectors. The stem is herbaceous, green with a tint of red, round, slightly hairy below, but smooth above, branching in forks and leafy. The leaves are alternate, in pairs, one generally smaller than the other, ovate, acuminate from three to six inches long, entire, thin, soft, and short stalked. The flowers are axillary, solitary, pendant, bell shaped, of a lurid or dingy purple above, and greenish below. The calyx is persistent, and bears the fruit, which is an ovate, black, shining, bilocular, many-seeded berry-like capsule, or pyxis, containing a sweetish pulp. If the root be used, it should be taken up in spring.

Datura stramonium. Stramonium is naturalized, but not indigenous. It is found in waste places; is an annual plant, rising two or three feet high, with a forked, spreading, leafy stem. The leaves are ovate, smooth, variously sinnuted and toothed, of a light dull-green hue; the flowers are axillary and solitary, situated in the forks; trumpet-shaped, about three inches long; the fruit is prickly, the size of a walnut, and full of dark-brown reniform seeds. The leaves should be gathered when the plant is in flower : the whole plant is officinal. It exhales a peculiar heavy odour. It is easily dried.

GENTIANACEA.-Menyanthis trifoliata. Buckbean, Marsh Trifoil. It is common on boggy or moist spongy soils. The leaves, which proceed from the rhizome, are supported on long footstalks furnished with broad sheathing stipules; they are trifoliate, the leaflets being nearly oval, smooth, somewhat fleshy, with irregularly marked but nearly entire margins. The footstalks are usually gathered with the rest of the leaf, which is inodorous, but aromatic and bitter to the taste. They are easily recognized, and are seldom adulterated.

MELANTHACEA.-Colchicum autumnale. Meadow Saffron. The cormus is now in its most perfect state; being large, plump, and firm, and bearing the young cormus in its rudimentary state; the last year's being now withered to a shrivelled shell, and separated from that of the present year. As soon as the cormi are dug up, they should be sliced transversely, and the slices dried separately on bibulous paper, at a temperature under 150°. The slices, when well dried, should be of a greyish white colour, and should become blue, when softened with distilled vinegar, and then touched with the spirituous tincture of guaiacum. Their acrimony should not be lessened by the drying. When the cormus is to be preserved entire, the brownish-black tegument should not be removed.

LILIACEA.Allium sativum. Garlic is generally cultivated, and the bulbs preserved in the aggregate, within the silvery skin which invests the whole.

PREPARATION OF CALOMEL.

BY M. SOUBEIRAN.

IN France and in England medical men almost exclusively employ calomel prepared with steam; it is found to be more active and more certain in its effects. The mode of preparation generally adopted is that of Joseph Jewel, with the modifications made by M. Ossian Henry. It consists in conducting steam, together with the vapour of calomel, into a large receiver. The manufacturing Chemists in France follow this process: I have adopted it for many years at the Pharmacie Centrale; but am far from being satisfied with it. The operation is difficult to conduct; it requires great expertness of manipulation, and too frequently is attended with accidents, which cause the loss of a great part of the product. Moreover, it must be admitted, that the calomel prepared with steam in France is neither so white nor so finely divided as that which is sent from England.

I have now to present, for communication to the Academy, a mode of preparation very superior to any other that is known to us. I would not occupy the attention of the learned Academy with a simple manufacturing process, if it was not one of a peculiar character, being applied to a product, in the preparation of which we have been unable, up to the present day, to compete with the English manufacturer.

For the vapour of water which is interposed between the particles of the vapour of calomel, and which prevents them from uniting, I substitute a current of air, which, passing over the heated calomel, enters the vapour as it forms, and causes it to condense in a subtle powder.* For this purpose, I heat the calomel in an earthen tube, passing through a furnace, and direct a constant current of air through the interior of the tube, by means of a small blower, so as to carry the vapour into a receiver. If the operation be conducted with a straight tube, a part of the calomel might be carried to a distance of more than twenty yards. To obviate this inconvenience, I cause the end of the tube to dip into water, and the calomel is thus wetted and precipitated in fine powder. This kind of termination to the apparatus is all that can be desired. It only remains for me to perfect the process by ascertaining the best form and material for the vessels in which the calomel is heated. I have not been able to meet with such, ready made, as combine the essential conditions, so that I am obliged to defer to another time the complete description of the process; but I may observe, that even my first attempts at the operation have proved quite successful.

I think the same principle of operation may be applied to the division of other volatile bodies.-Comptes Rendus.

Dr. Christison alludes to an analogous process in his Dispensatory which he gives on the authority of Mr. Dann, of Stuttgardt, p. 525.—ED.

ON THE METALLIC ACIDS.

BY M. E. FREMY.

(Extracted by the Author from a Memoir presented to the Academy of Sciences.)

IN submitting the metallic acids to a general examination, I have found some new combinations of metals with oxygen; and new salts, remarkable for their beautiful crystalline forms. The metallic acids may be divided into two classes: in the first are placed those which result from the immediate combination of metals with oxygen, and which dissolve in the cold in alkalies; in the second, the acids which are formed when a metallic oxide is exposed to the simultaneous influence of an alkali and of an oxidizing body.

The metallic acids, which are produced by these two means, present in their properties essential differences. The first are in general stable, and with bases may be formed into well defined and crystallizable salts; the second, on the contrary, are easily decomposed, and lose a part of their oxygen under feeble influences.

To give an example of the first class of acids I have chosen the last combination of tin with oxygen, which has received the name of stannic acid; and to characterise the second class of acids, I have studied a new combination of iron with oxygen, which I have named ferric acid. In taking, for examples, the metallic acids belonging to important metals, I have intended to indicate the existence of similar combinations among the metals less known.

I have commenced with the examination of ferric acid. I have given a detailed account, in my memoir, of the different means which I have employed to prepare the ferrates. The combinations of ferric acid with bases may be obtained either in the dry or in the humid way. The dry way consists in calcining the peroxide of potassium with sesquioxide of iron in a vessel which will exercise no action on the ferrate. The means by which the ferrate of potash may be most easily obtained in the dry way, is to throw nitre, dried and reduced to powder, on iron filings, previously made red hot; five parts of iron and ten of nitre should be used. A red mass is thus obtained, which contains a large quantity of ferrate of potash. I have prepared the ferrate of potash in the humid way, by availing myself of the result of M. Berthier's experiments on the action which chlorine exercises on the metallic oxides. It is by passing chlorine through a very concentrated solution of potash, holding the hydrate of peroxide of iron in suspension, that I produce the ferrate of potash by the humid way. I enter, at this part, into some details on the action