oxygen. While it retains the black colour, the solution has 27 parts of oxygen to 73 parts of iron; but by being exposed to the atmospheric air for any length of time, it becomes fully oxygenated, assumes a reddish rusty colour, and then it contains 48 parts of oxygen to 52 parts of metal. When the timber of a house or ship is thus impregnated with iron, if it be rubbed over with oil and any of the alkaline salts mixed together, or with 'common soap, it will become very hard, and almost impenetrable. A compound of hog's lard, camphor, and lead, will have nearly the same effect. Any other substance, that will prevent the iron from being over oxydized, will be as effectual. For it is well known, that iron is in itself harmless, but becomes corrosive, when combined with a very large portion of oxygen: therefore to saturate with iron, and at the same time to prevent its being superoxydized, is all the little difficulty that is here to be encountered.'

Mr. McWilliam has devoted a solitary chapter to the ravages committed on timber by worms; but a great portion of curious matter on the nature and habits of these destructive insects is to be found in the volumes on Entomology by Messrs. Kirby and Spence. It often happens that a piece of timber is completely destroyed in the inside, with scarcely any indication of decay without; so that the evil is not suspected till it has become too deeply seated to be removed by any external application. The essential oil of turpentine, lime-water, and a strong decoction of garlic in common water, are effective to the extent in which they are absorbed but the great difficulty is access to the enemy. Those forest-trees which are hard, or have bitter juices, are least liable to these insects: they scarcely ever touch box or ebony; and it is asserted that, in addition to its other admirable properties, the larch has never been known to be affected by the larvæ of insects.

器

Having taken this extensive analytical view of the body of the work, we can devote but little room to the Appendix; which is copious, and contains much miscellaneous matter, not relating to the dissertation itself but to the general state of the forests in the United Empire. Mr. McWilliam strenuously recommends an extension of planting, and offers a variety of valuable suggestions on the cultivation of timber. He presents us with a number of calculations, and some documents, to prove that the quantity of our domestic timber is diminished, and the demand for it increased; adding, and perhaps truly, that agriculture itself has not been benefited by disforesting large tracts of land, because, in consequence of the loss of these very woods, many districts are now exposed and bleak, and rendered barren by the exposure, which were once cultivated under the shelter of their antient woods. If those mountain

ous districts be planted on which corn will not pay for culture, a capital will thus be created without any loss of rent; and the immediate expence is little, while the future remuneration will be great. It is unnecessary to dissuade proprietors from planting good arable land: but many dreary and unprofitable wastes, many naked hills and unwholesome bogs, might advantageously be converted into wood-land; and the utmost possible encouragement is here given, for Mr. McW. contends that wood may be cultivated in every soil and climate, from the sea-beach to the mountain-top, from the equator almost to the pole. The adaptation of trees to soil and situation appears to be the principal object. He remarks that those which prosper best on steril soil have generally firm, hard, but slender roots; while those which require more fertile soil have their roots usually more thick, plump, and, many of them, spungy and soft. Those which require least or most shelter may be generally known at once by the size of their leaves and the flexibility of their footstalks, for trees in general require shade and shelter in proportion to the size of their leaves: the broader the leaf, the more protection is necessary.'

We cannot take leave of this writer without thanking him for the instruction as well as the amusement which he has afforded us. An enthusiast himself, his zeal to inspire others with the same enthusiasm for planting is meritorious: every personal and patriotic feeling is invoked-private interest and public benefit-to stimulate proprietors of land to the good work; and, although the present volume does not profess to give minute and detailed instructions for planting, we should certainly recommend it to attention not only from builders with reference to the disease of the Dry Rot, but from those gentlemen, likewise, who are preparing to furnish the materials for building, by redeeming the sterility of their wastes and clothing their hills with timber.

ART. IV. Mr. Stewart's Elements of the Philosophy of the Human Mind.

FROM

[Article concluded from p. 272.]

ROM the observations which have already been made, we think that the reader will sufficiently perceive with what modification we are to admit the strictures of Mr. Stewart on the doctrines of Dr. Beddoes and Professor Leslie, with respect to the nature of demonstrative evidence. The error of Dr. Beddoes certainly consisted in the view which he took

not of the basis but the superstructure of geometrical reasoning. Nothing can well be more evident than the principle assumed by this author, that our notions of extension and figure are derived from the senses: but it does not therefore follow that it is desirable to change our modes of investigation and instruction on these subjects, and adopt the experimental method which he recommends. We are particularly surprized, however, that, in the whole of this section, Mr. Stewart has not once adverted to the leading and characteristic property of the objects of mathematical investigation, that they are all susceptible of measurement: though, perhaps, such a remark would have looked too much like an appeal to fact and observation. He does, indeed, take a slight notice afterward, in passing, of this circumstance, when speaking of the application of theoretical conclusions to practice; yet it is of very considerable importance to attend to it, in order to attain correct ideas of the actual process of the mind in the theoretical investigations themselves, more especially when the algebraical modes of analysis are employed.

The next chapter is entirely occupied with an elaborate examination of the Aristotelian logic; the principal object of which is to shew that the syllogistic theory is utterly futile and absurd. This will be allowed to be a sufficiently bold thesis; yet it does not appear to us that much has been added by the author to the objections which had previously been advanced by Mr. Locke and Dr. Campbell, and, as we conceive, very satisfactorily refuted by various eminent writers. "Mr. Stewart, however, thinks it was not without good reason that Dr. Campbell hazarded the epigrammatic but unanswerable remark, that there is always some radical defect in a syllogism which is not chargeable with that species of sophism known among logicians by the name of petitio principii, or a begging of the question,' Now we cannot refrain from saying that Dr. C. might have spared this unanswerable remark. On farther reflection, he might have found, as we conceive that every one else will find who understands the real nature and object of the syllogism, that his observation would have been equally correct and still more epigrammatic, though not so well adapted to his purpose of crying down the syllogistic theory, if he had proceeded to affirm that the syllogism derives its conclusiveness from this same petitio principii. In every real argument, the labour is to establish not the truth. of the conclusion, but the truth of the premises, from which that of the conclusion follows of course, as being necessarily involved in them: so that the syllogism may properly be considered as merely the statement of an argument, not the

argument

argument itself. In the statement, the truth of the premises is assumed, and the conclusion appears to be actually contained in them; and the use of this artificial arrangement is to make it appear that, if the premises be admitted, the conclusion must be admitted likewise. The business, then, is to prove the premises. This position may be illustrated by a well known example. Cicero is defending Milo, and the argument of his defence may be thus concisely stated:-A man is justified in killing another who lies in wait to murder him: Clodius lay in, wait, to kill Milo; therefore Milo was justified in killing Clodius. This is a regular syllogism; and it cannot be doubted that the conclusion is actually contained in the premises: so that, if this were the argument itself, and not merely the statement of the argument, it would involve the petitio principii here laid to its charge: - but the whole of Cicero's labour in this celebrated oration is to prove the truth of the premises; and, when this is once made out, his object is accomplished. We apprehend that this view of the true application of the syllogism may be of considerable use in rightly estimating some of the plausible, but fallacious, objections which are brought against it by the present and other writers.

Mr. Stewart's first objection to the syllogistic theory is founded on the demonstrations by which the validity of the various technical rules of mood and figure is established.

t

These demonstrations,' he says, 'proceed on the obviously false supposition of its being possible to add to the force of demonstrative evidence.' Nothing, certainly, can be more completely erroneous than this supposition: but we are at a loss to comprehend in what way it is involved in the demonstrations in question. To suppose that it is would be to ascribe an absurdity to their author too glaring to be admitted, for these demonstrations themselves are nothing more than a series of syllogisms. The fact is, that this objection proceeds on an entire misconception of the real nature and object of the syllogism: which object is not to furnish a new instrument of reasoning, or to add any thing to the force of demonstrative evidence: but to develop those principles of the human understanding on which all accurate reasoning must ever proceed; and to present a clear and exact statement, in words at length, of the process which is tacitly, but really, performed by the mind in the conduct of an argument. The syllogism, therefore, is justly represented not as an invention but as a discovery; being nothing more than the unfolding of those principles on which all correct reasoning, from the creation of the world, must have been founded:

which is rendered evident by the undeniable fact that every conclusive argument admits of being stated in the syllogistic form.

Mr. Stewart's objections to the syllogistic theory seem, in many instances, to proceed on a conception of its nature and intention that is perfectly erroneous, and for the last two hundred years at least has been universally exploded; namely, that it was the object of the syllogism to assist in the discovery of truth.

For my own part,' says he, (p. 274.) I cannot help being of opinion with Lord Monboddo (who certainly was not wanting in a due respect for the authority of Aristotle) that the syllogistic theory would have accorded much better with the doctrine of Plato, concerning general ideas, than with that held on the same subject by the founder of the Peripatetic school. To maintain that in all demonstration we argue from generals to particulars, and at the same time to assert that the necessary progress of our knowledge is from particulars to generals by a gradual induction from the informations of sense, do not appear to an ordinary understanding to be very congruous parts of the same system.'

Nor would they be so, if demonstration were the method by which we discovered truth: but nothing can be more evident than that every truly synthetic demonstration implies that the conclusion has been previously ascertained in the way of analysis. By analysis, we proceed from particulars to generals, by a gradual induction from the informations of sense, or from whatever other source we derive the materials of our knowlege. Where is the wonder, then, that in demonstration we should reverse the process, and advance from generals to particulars?

Another objection to this whole theory we shall state in Mr. Stewart's words, and then leave it to its own merits:

< The fundamental idea on which this philosopher (Aristotle) evidently proceeded, and in which he has been too implicitly followed by many even of those who have rejected his' syllogistic theory, takes for granted that the discovery of truth chiefly depends on the reasoning faculty, and that it is the comparative strength of this faculty which constitutes the intellectual superiority of one man above another. The similarity between the words reason and reasoning, of which I formerly took notice, and the confusion which it has occasioned in their appropriate meanings, has contributed powerfully to encourage and to perpetuate this unfortunate mistake. If I do not greatly deceive myself, it will be found on an accurate examination of the subject, that of the different elements which enter into the composition of reason, in the most enlarged acceptation of that word, the power of carrying on long processes of reasoning or deduction is in point of importance one of the least.'

'Among