a current is produced in a wire by simply moving it over a galvanometer, and states that scarcely any piece of metal can be moved in contact with others without an electric current existing between them.

By the rotation of electro-magnets of insulated wire before the poles of a permanent magnet, a current is induced in the wire when opposite the poles of the magnet, and another in the reverse direction, when the armatures are at right angles to the poles; thus a succession of currents are obtained by means of a ratchet and wheel breaking and renewing the connexion of the two armatures. If very fine insulated wire is used in the armatures an "intensity" current is obtained, and shocks are produced; if thick wire is employed, a “quantity” current is obtained, and by allowing one end of the wire to rub against the break, and thus cut off the cross current from the handles, a current in one direction only is obtained, in both the intensity or quantity inductors, the former precisely corresponding to the effects from the primary coil already described. By changing the thickness of the wires we can obtain all the phenomena of current electricity, without the use of any battery whatever, and either quantity or intensity effects from the same source. It possesses the advantages of cleanliness, order, certainty and variety of effect, but these are more than counterbalanced by costliness, cumbersomeness, and manual labour.

The last form of apparatus noticed was the "Hydro-Electric Chain," which simply consists of aseries of batteries composed of zinc and gilt wire, imperfectly insulated, each link alternating with the next, these varying in number from 12 to 120 alternations (vide fig. 11). Where muscular contraction was not required, Dr. Edwards considered this a very valuable means of applying a small but continuous stream of electricity, and he showed by experiment, that the decomposing and magnetizing effects, when the body is included in the circuit, are equal to those produced by an equal number of moderately sized battery plates-thus proving, that these results are limited in all cases to the conducting power of any substance placed within the circuit; and further that the amount of quantity electricity produced by these small generating cells is as large as the limited conducting power of the epidermis is capable of transmitting through the human body.

The subject was illustrated with experiments, apparatus and diagrams; and the lecturer entered into several explanations after the lecture.

ORIGINAL AND EXTRACTED ARTICLES.

EXAMINATION OF PAVON'S COLLECTION OF PERUVIAN
BARKS CONTAINED IN THE BRITISH MUSEUM.
BY JOHN ELIOT HOWARD, ESQ.
(Concluded from page 235.)

OBSERVATIONS ON THE FALSE BARKS IN PAVON'S COLLECTION.

BARKS of the genus Cascarilla (Weddell) seem to me to have constituted the "White Quinquinas" of an early period. "The second species at Loxa," according to M. Jos. Jussieu, "comprehends the white quinquinas to the number of four; the common character of which, distinct from the preceding, is to have great leaves, rounded and hairy-the flowers red, very fragrant, bristled with hairs in the interior, the fruit long, and the bark externally white. In the two former, the bark has the internal substance verging on red; it is a little bitter, and possesses, when recent, a very inferior febrifuge property, which it soon loses. In the two others, it is all white, insipid, and without efficacy. These are the kinds the flowers of which exhale the sweetest perfume, by a compensation of nature, which appears to have transported into the flowers the aromatic principles which she refuses to the barks."

1. Cascarilla magnifolia. Weddell.

The fragrance of the Cascarilla magnifolia is specially noticed by Weddell, who wishes it on that account introduced into our conservatories, and which merited the name "Flor d'Azahar," or "Orange Flower." Under this first head range the following in Pavon's collection :

No. 38. C. magnifolia. Fl. Peruv.

Some difficulty has arisen in the identification of this bark, from the varying appearance which it presents, but the specimens brought by Dr. Weddell show these all to belong to one tree, which furnishes the Quina nova of commerce, a spurious bark which, according to Batka,† "till 1805 maintained its genuineness in the North American trade as red bark, and since 1820 in the collections of Denmark as Cinchona rubra." I conclude from the description that this is also the China nova Surinamensis, of which Buchner says, "this spurious bark, which can be obtained at a very low price, is generally employed for adulterating the better sorts, especially the Calisaya bark and Carthagena bark." No spurious bark that has fallen under my observation has been imported in such large quantities as this, and when reduced to powder its cinnamon colour would cause it easily to be mistaken for a good bark. According to Ruiz,§ it constituted the bulk of the early importations sent by Mutis from St. Fé, and this fact is admitted by his disciple Zea. It is therefore possible that the importation of so much worthless bark might cause the Quina naranjada to be also looked on with suspicion, and burnt, which seems to have been a practice followed with the inferior barks at Cadiz. The same fate befel a quantity of the Quina nova at Havre a year or two since. Some small specimens came under my notice amongst the first samples of bark sent in the renewed importations made from Santa Fé de Bogota; and it has since been more largely imported from that quarter, and though sold at an extremely low price, has not ceased to come. If named according to the white epidermis, this bark may well range among the white quinquinas; if regarded according to the general tint of the outer coat (as in samples given me by Dr. Weddell, and in one from Peru which I obtained from commerce in the year 1838), it may be called, as by Ruiz and Pavon, amarillo or yellow; if the purple red, or sometimes pomegranate colour of the surface of the derm (denuded of outer coat) be the general character, it may

† Pharm. Journal, vol. xi., p. 321.

Ibid., vol. xi., p. 167.

"To the great prejudice of the royal treasury, the thick bark (cortezones) of the Roxa alone entered with absolute preference into his (Mutis's) immense cuttings; then the amarilla

*

and the naranjada or tunita, which he did not know till long afterwards, as it continued despised until he began to know the reprobation of his shipments of red barks (cortezones roxos.)" Memoria de las Virtudes y usos de la raiz de la Planta Llamada Yallhoy, &c. Par Don H. Ruiz. Madrid, 1805.

"The first species known, which obtained great estimation for its prodigious effects in intermittents, was the naranjada. This species being extremely rare, they substituted in its place the barks of the tree which appeared most to resemble it. This was, to the disgrace of those times of ignorance, the Quina roxa, the properties of which being then unknown and much different from the naranjada, gave occasion to the havoc (los estragos) which history has transmitted to us."-Zea, as quoted by Ruiz, Suplemento, p. 36.

ག་ "The cinchonæ, as other trees, when they begin to fructify, contain without contradiction their juices and principles in a state of maturity. At this epoch the barks are in a fit state to be gathered, as is practised in Caxanua and Uritusinga, mountains of Loxa.

"When the trunks or boughs are covered with multiplied layers of bark, according to the number of years they have attained, the external layers are without succulence, too dry, crusty, hardened and woody-fungous or shrivelled, and the internal parts have sap only in those parts by which the sap or nutritious juice, by means of which the plant grows, ascends or descends, and this smallest part of an old bark (cortezon) is the only useful part, since all the rest is not only useless but hurtful on account of styticity, or other contrary qualities, which the barks (cortezas) have in their state of perfection, and when they are free from the multitude of extraneous bodies which have adhered to the thick barks (cortezones) for so many years. For this reason they have burnt, by order of the king, on the heights of San Bernard of Madrid, considerable quantities of thick barks (cortezones). The barks of the young branches have not their juices in a state of so great activity as those of medium size which have arrived at the state of maturity, yet it is undeniable that they are more efficacious than the cortezones with so many outer coats, since they are free from so many thick and shrivelled coverings, formed by time and embrowned by the heat of the sun, increased by the lichens and other extraneous bodies, and rotted by the unnumbered rains which have fallen upon them, as happens with the boughs of other trees."-Suplemento,

p. 41.

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acquire, as it did here, the name pomegranate bark ;" and if the general red coloured substance be considered, it may be named (as it was by Mutis) roxa or red.†

I have only to add, in confirmation of a notice by Pelletier and Caventou,‡ that this bark (though useless for medicinal purposes) is not without a minute proportion of alkaloid (“en quantité infiniment petite," P. and C.). MM. Pelletier and Caventou obtained about .0015 per cent. of alkaloid, and I have met with a like proportion, soluble in ether, and giving, like quinine, a decided green colour with chlorine and ammonia.

5. Cascarilla Riveroana. Var. a.

This is the C. oblongifolia of Lambert (but not of Mutis), with leaves pubescent on the under side.

No. 15. C. Azahar Macho de Loxa. Var. ß.

No. 18 and *30. C. Azahar hembra, vulgo de Jaen de Loxa.

No. **8. C. quina Azahar macho de Jaen Loxa.

As these barks are scarcely to be found in commerce, I shall not add to the notices of them already given in the table.

9. Cuscarilla Pavonii.

This is found among the specimens of wood, No. 17, exhibiting the very peculiar hollow caused by the contraction of the pith, on which account the name Cinchona cava was given it by Ruiz and Pavon.

18. Cascarilla macrocarpa.

No. **6. Quina blanca. This has been already sufficiently described by others. Its contents are similar to those of the Quina roxa, and the alkaloid (which has been called Blanquinine), gives a decided green precipitate with chlorine and ammonia.

No. 12. C. margarita de Loxa. Of this I possess a botanical specimen, marked by Pavon "Chinchona var. Margarita de Jaen." This was given me by Dr. Weddell as Cascarilla magnifolia. It appears, therefore, to be a variety slightly differing (as in the bark, &c.) from the typical form.

No. 8. C. rosea del Peru.

Lasionema roseum.

No. 5. C. cascarilla Taron-taron de Loxa.
This bark is not now met with in commerce.

Condaminea tinctoria, D. C.

No. 14. C. laccifera del Peru, p. a la roxa de Mutis.

This curious bark is described by Guibourt as his Ecorce de Paraguatan, of which he has given me a specimen. I have found it in English commerce, but it possesses no peculiar interest, except as viewed with the microscope.

Nauclea Cinchonæ, D. C.

No. 32. C. globosa, unas de Gato, vel acullata de Guayaquil.

No. **5. C. globosa, sp. nova inedit. de Loxa.

The peculiar toughness of the fibre would prevent its being intentionally mixed with good bark, but it is at times accidentally intermingled.

False (?) barks, origin unknown.

No. 26. C. cascarilla o quina de Nagenal de Loxa.

"It is beyond contradiction that the cinchona oblongifolia of Dr. Mutis constitutes one and the same species with our cinchona magnifolia, or lutescens of Ruiz."-Suplemento, p. 53.

Journ. de Pharm. for 1821.

No. 29. C. cascarilla con hojus de Palton de Loxa.

No. **1. C. viridiflora, sp. nov. de Peru, inedita No. **2. A second specimen of the above.

I have confined my attention, in this survey, to the false barks represented in Pavon's collection. Others are referred to by Condamine in a passage quoted above (vol. xi., p. 492). A bark similar (as to the styptic taste) to the Alizier there mentioned is mixed very frequently with the canuto of C. calisaya, and is probably the product of Laplacea quino-derma, Weddell. It has come, but very rarely, with the tabla, from which it is more easily distinguished. The cascarilla carua is also, I think, frequently intermingled with the canuto of calisaya.

The characteristic difference noticed by Weddell is, that "in the dry state the false barks are in general distinguished with the greatest ease from those rightly called Quinquinas, by the hardness and the constant persistance of their cellular tunic, and by the very woody nature of the liber." (Histoire, &c., p. 78.)

CONCLUSION.

In bringing to a determination my remarks on the collection of Pavon, it remains for me simply to recal to the reader's notice that I have only touched incidentally on the barks of Bolivia and those of New Granada, which are not represented in this collection. It is evident (as I have in part attempted to show) that some very useful species of bark growing in Peru were known to these botanists, which have since been lost sight of, and which the activity of commerce will probably again rescue from oblivion. As to the different kinds of bark which I have found in commerce and described, I have it in contemplation to present specimens to the museum of Dr. Pereira, that they may remain for permanent reference and illustration of the observations in this series of papers.

Since the above was in type, I have had the opportunity of examining specimens recently sent by Dr. Winckler to Dr. Pereira, which afford additional elucidation of the names used in Germany.

China Jaen fusca, China de Para, contains paracin,—is “Para bark.”
China Jaen nigricans,—is “ Ash bark," produce of C. ovata.

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China Jaen pallida,-appears to be the quill of C. Pelletierana.

China Huamalies,—a brown bark, partially resembling "Carabaya bark." China flava fibrosa,—a brown bark, not now found in commerce, except as mixed with other sorts.

China Huanuco,-inferior Loxa, not the "Grey bark" of English commerce.
China rubiginosa opt.,-is the "hard coated ovata" described above.
China nova Surinamensis,—is "Quina nova.'

ADDENDA ET CORRIGENDA.

Vol. xi., p. 494, et alia, for Quinidin read Quinidine.

Vol. xi., p. 561 (also vol. xii. p. 125), for Ristolfo read Restrepo.

Vol. xi., p. 562, line 26, for C. lanceolata of Mutis read lancifolia of Mutis.

Vol. xii., p. 59-The coloured alkaloid of C. Pelletierana so much resembles paracin in its properties as to lead me to think them the same. It is, however, a crystallizable alkaloid, and needs further investigation.

It is interesting to consider what is the botanical relationship of barks containing paracin, or rather aricine-I have already several kinds possessing this peculiarity.-See also Riegel's Observations, Pharm. Journ., vol. xii., p. 251.

Vol. xii., p. 234, line 36, transpose the ( ;) from after the word "France" to before the words "in France."

A FALSE ISINGLASS FROM PARA.

A SUBSTANCE has lately been imported, under the name of Isinglass, which, on examination, proves not to be isinglass, but the dried ovary of a large fish.

Two boxes were imported : they did not contain more than 14 or 16 lbs. A similar article has been before imported into London. It consists of bunches of the size and shape of the subjoined figure. They somewhat resemble a bunch of grapes; and consist of ovoid or rounded masses, attached by peduncles to a central axis; by immersion in water this axis is found to consist of a convoluted membrane, to one side only of which these ovoid masses are attached.

A very superficial examination of this so-called isinglass, proves that it is neither the swimming bladder of a fish, nor is it gelatinous; but it is in reality the ovary of some large fish, and is of an albuminous nature. When soaked in water its fishy odour becomes very obvious.

The ovoid masses are ova. They are highly vascular on the surface, and are filled with an animal substance of a yellow colour. In general appearance they resemble the vitellus of a shark or ray.

The Sudis Gigas, a large osseous fish, upwards of six feet in length, is found at Para. Its flesh is dried, salted, and eaten by the lower classes; and its swimming bladder constitutes one of the kinds of Brazilian isinglass imported into London. It is probable, therefore, that the ovary of this fish constitutes the false isinglass in question. If not from this fish, it is probably obtained from some allied genus (as Amia), of highly organized osseous fishes.

False Isinglass from Para.-(Natural size.)