The combination of platina and iron is very powerful, and has the advantage of permitting the application of great heat. That of platina and silver is readily applied to exhibit the inverse experiment, i. e. the motion of the thermoelectrics on the approach of a magnet. A silver wire bent into the form A is connected with a platina wire B into the form C E D F, either by soldering or by fine platina wire; the whole is suspended from a point D. On heating one extremity E, and applying the pole of a magnet to F, the apparatus revolves from left to right, or vice versa, according as the pole of the magnet is N or S. The apparatus I have used for the purpose weighs nine grains : indeed I know no limit to its minuteness.

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The annexed figure represents an arrangement for producing a perpetual rotation, by means of platina and silver wires poised upon a magnet, and heated by a spirit-lamp. A BDC platina wire; Abc defC, silver wire; c N, support of the wires; N S, magnet; L, spirit-lamp.

The platina wire being considerably thicker than the silver, the part A B will balance the projecting part of the silver wire def C. A wire is attached to d e at right angles with a small weight to counterbalance B D C.

P. S. The electromagnetic multiplier mentioned in your number for June, is, I perceive, a similar instrument to that which I used and described as a Galvanoscope two years and a half since, in a paper published in our Cambridge Transactions, and with which all my present experiments were made. Very sincerely yours,

J. CUMMING.

ARTICLE III.

On the Classification of Poisons.

[THIS article is taken from a work lately published on Medical Jurisprudence, by J. A. Paris, MD. FRS. &c. and J. S. M. Fonblanque, Esq. Barrister at Law. It would not be consistent with our plan to enter minutely into an account of a work of this nature. It contains, however, so much curious matter connected with chemical science, on the subject of nuisances and poisons, that we intend, in a future number, to give from it, and other sources, a general and comprehensive view of the methods of examining substances suspected to contain poison, with observations and additional experiments on the subject. In the mean time, we present the reader with the classification of poisons adopted by the above-mentioned authors.-Edit.]

Poisonous substances have been very differently arranged by different authors, each appearing to have adopted a classification best suited to promote the particular views and objects of his own pursuit; thus, the botanist and chemist, engaged in the examination of the physical characters by which poisons may be individually distinguished and identified, have very judiciously erected their system upon the basis of natural history. The pathologist, whose leading object is the investigation of the morbid effects which follow the administration of these agents, with equal propriety and justice, prefers a classification deduced from a generalization of the symptoms they are found to occasion; while the physiologist, who seeks to ascertain through what organs, and by what mechanism, they destroy life, may reasonably expected to arrange the different poisons under divisions corresponding with the results of so interesting an inquiry.

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To meet the comprehensive views of the forensic toxicologist, an arrangement would seem to be required, that should at once embrace the several objects which we have just enumerated;

for the data from which the proof of poisoning is to be inferred, are, as we have often stated, highly complicated in their relations. No such classification, however, can be accomplished, and we are therefore compelled to select one which may approach the nearest to our imaginary fabric. That which was proposed by Fodéré, and adopted, with some trivial alteration in the order of succession of the classes, by Orfila, in his celebrated system of toxicology, although it has many defects and some errors, nevertheless merits the preference of the forensic physician; its basis is strictly pathological, and yet it distributes the different poisons, with some few and unimportant exceptions, in an order corresponding with that of their natural history.

The first two classes, for instance, present us with substances of a mineral origin; the third and fourth, with those which are principally of a vegetable nature; and the sixth, with objects chiefly belonging to the animal kingdom. The importance of acknowledging a division, which has a reference to the three great kingdoms of Nature, is perhaps greater than the reader may anticipate; for in enumerating the various experiments to be instituted for the detection of poisons, we are, by such an arrangement, enabled to bring together a connected series of processes, nearly allied to, intimately connected with, and in some respects, mutually dependant upon each other.

The following is the arrangement of Fodéré as modified by Orfila; viz. Cl. I. Corrosive, or Escharotic poisons. Cl. II. Astringent poisons. Cl. III. Acrid or Rubefacient poisons. Cl. IV. Narcotic or Stupefying poisons. Cl. V. Narotico-Acrid poisons. And Cl. VI. Septic or Putrefying poisons.

Class I. Corrosive or Escharotic Poisons. Such as corrode and burn the textures to which they are applied. When internally administered, they give origin to the following symptoms: violent pain, accompanied with a sense of heat and burning in the stomach, and throughout the whole extent of the alimentary canal; frequent vomitings, often sanguineous, and alternating with bloody diarrhoea, with or without tenesmus; the pulse hard, small, frequent, and at length imperceptible; an icy coldness of the body; cold sweats; a great anxiety and oppression at the præcordia; and hiccup. Sometimes the heat of the skin is intense, the thirst inextinguishable, and the unhappy patient is tormented with Dysuria and Ischuria, violent cramps in the extremities, and horrid convulsions, which are relieved only by death. Such are the general symptoms by which this species of poisoning is characterised; the rapidity with which the symptoms terminate their course will depend upon the violence of the dose, and the particular species of poison which has produced them: there are, moreover, other symptoms which will be more conveniently described, when we come to speak of the effects of corrosive poisons individually. In this class are

ranked the following substances:-METALS. I. Arsenic. I. Arsenious Acid, or White Oxide of Arsenic. 2. Arsenites, or Combinations of that Acid with salifiable Bases. 3. Arsenic Acid. 4. Arseniates, or Combinations of the preceding Acid with the Bases. 5. Sulphurets of Arsenic, or Orpiment and Realgar.-II. Mercury. 1. Corrosive Sublimate of Mercury, or Oxymuriate of Mercury. 2. Red Oxide of Mercury. 3. Red Precipitate, or Nitric Oxide of Mercury. 4. Other preparations of Mercury-III. Antimony. 1. Tartarized Antimony, or Tartar Emetic. 2. Oxide of Antimony. 3. Antimonial Wine. 4. Muriate of Antimony, or Butter of Antimony.-IV. Copper. 1. Blue Vitriol, or Sulphate of Copper. 2. Verdegris. 3. Oxide of Copper. 4. Other preparations of Copper.-V. Tin. 1. Muriate of Tin.-VI. Zinc. 1. Sulphate of Zinc, or White Vitriol. 2. Oxide of Zinc.-VII. Silver. 1. Nitrate of Silver, or Lunar Caustic. The Concentrated Acids. 1. Sulphuric. 2. Muriatic. 3. Nitric. 4. Phosphoric, &c.-Hot Liquids. 1. Boiling Water. 2. Melted Lead.-The Caustic Alkalies. 1. Potass. 2. Soda. 3. Ammonia.-The Caustic Alkaline Earths. 1. Lime. 2. Baryta. 3. Muriate and Carbonate of Baryta. Cantharides. Phosphorus.

Class II. Astringent Poisons.-They occasion a remarkable and unrelenting constriction of the great intestines, especially the colon, so as to resist the operation of the most powerful cathartic remedies. Violent cholics ensue, and partial paralysis; in the end if the dose be sufficiently large, or if small doses have been frequently repeated, they will excite inflammation of the alimentary canal, but it is not succeeded by that disorganization which generally characterises the operation of poisons belonging to the preceding division. We rank under the present class only the preparations of lead, viz. 1. Acetate of Lead, or Sugar of Lead; 2. Oxides of Lead, Red Lead, Litharge; 3. Various saturnine impregnations.

Class III. Acrid or Rubefacient Poisons.-These poisons are known by their producing an acrid taste, more or less pungent and bitter; a burning heat, and considerable dryness in the mouth and fauces; and a constriction, more or less painful, in the throat. Acute pains are, after a short interval, experienced in the stomach and bowels, which are quickly followed by copious vomiting and purging, and which continue, with the most painful efforts, long after the alimentary canal has been completely evacuated. A few hours after, phenomena are observed, which indicate a lesion of the nervous system, such as vertigo, dilated pupils, dejection, insensibility, laborious respiration, and death. The lesions of texture, occasioned by the action of acrid poisons, have the greatest analogy to those produced by corrosive poisons; in fact, says M. Orfila, we do not hesitate to declare, that there exists a perfect identity between

the alterations of the digestive canal produced by the poisons of these two classes, when introduced into the stomach." The substances included under this class belong, for the most part, to the vegetable kingdom, such as scammony, camboge, black and white hellebore, bryony, euphorbium, seeds of the ricinus, iatropa curcas (Indian nut), croton tiglium, squill, aconite, &c. &c.

Class IV. Narcotic or Stupefying Poisons.-Such as occasion stupor, drowsiness, paralysis, or apoplexy, and convulsions. They do not produce any change in the structure of parts to which they are applied. M. Orfila has satisfactorily ascertained that no alteration can be discovered on dissection in the digestive canal of persons who have swallowed any one of the poisonous substances of this class.

Class V. Narcotico-Acrid Poisons.-This division, as its name implies, is intended to receive such substances as produce the united effects of those belonging to the two preceding classes, acting for instance at the same time, as narcotics and rubefacients. Amongst the articles of this class, the following may be enumerated, Belladonna, stramonium, tobacco, foxglove, hemlock, nux vomica, camphor, cocculus indicus, certain mushrooms, alcohol, &c. &c.

Class VI. Septic and Putrefying Poisons. By this term are included those poisons which, according to Orfila, "occasion a general debility, dissolution of the humours, and syncope, but which do not, in general, alter the intellectual faculties." The articles of this class belong almost entirely to the animal kingdom, with the exception perhaps of a few gaseous compounds, and the spurred rye, or ergot, viz. venomous animals; animals whose fluids have been depraved by antecedent disease; the poison of fishes; substances in a state of putridity; spurred rye, or ergot.

Such is the classification which, for reasons already stated, it is our intention to adopt on the present occasion. We shall, however, in an additional chapter, under the title of “Aërial Poisons," treat of those substances which are exclusively capable of acting upon the body through the medium of the atmosphere, or which require to be in a state of vapour, or gas, to ensure their operation.

With regard to the classification of Fodéré and Orfila, we must here observe, that we follow it only conventionally, and that while we acknowledge it as being very convenient for the consideration of poisons, in reference to their forensic relations, yet we must not be considered as insensible to its many defects and fallacies. In the first place, it has little or no reference to the enlarged views of the modern physiologist, respecting the " modus operandi" of poisons; nor indeed is its construction susceptible of such modifications and improvements, as can