and observing how far the facts at present ascertained respect ing their situation support or controvert the doctrine of the single creation of each kind. The conclusions of Dr. P. are decidedly in favour of his hypothesis. It does not appear that any animal was originally common to the warm parts of the old and the new world; nor that any European species are aboriginal in America, which are inhabitants of the northern parts of each continent. It is farther stated that, with the exception of the dog, which seems to have accompanied the first settlers in almost all parts of the world, the whole stock of Australasian quadrupeds is peculiar, and strikingly different from those that exist in other countries. Although some dif ficulties remain respecting the manner in which remote islands receive their animal population, yet, for the most part, the facts render it probable that they were transplanted by accidental circumstances, and all originated from one common pair.

The same mode of reasoning, which has been used with respect to inferior animals, is now applied to man; and the author proceeds to inquire, how the more remote and insulated parts of the earth can be supposed to have been peopled from the original stock, in the earliest ages, before the art of naviga tion could afford them any mode of migration. The question is very curious and interesting, and can only be answered by conjectures: but, on the whole, we do not appear to have sufficient ground for deviating from the same mode of reasoning which we have applied to the inferior animals. The islands of the Pacific Ocean, which are situated at the greatest distance from the main land, and the most widely dispersed from each other, are all inhabited by tribes that seem to have sprung from the same common stock; and several remarkable circumstances would lead us to conclude, that the native Americans originally passed over to the new continent from the eastern parts of Asia.

Having thus endeavoured to shew that the human race must be considered as composing only one species, and derived from one common pair, our next subject of inquiry is to ascertain in what manner the varieties which we now observe were originally produced. The difference of complexion is first investigated; and the author discusses at length the opinion, whether the dark hue of the inhabitants of the torrid zone depends on the effect of the sun's rays. This idea he controverts with much ingenuity and research: adducing facts to prove that, when persons of a white complexion have migrated into warm climates, and their posterity have remained there for a number of successive generations, their colour never experiences any permanent change; and that any degree of brownness

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brownness which is the consequence of exposure to the sun, or of hard labour, is not transmitted to the posterity. Other proofs of the same position are derived from the circumstance of particular tribes existing in very hot climates, who have never acquired the dark hue of their neighbours; and, on the contrary, of some colder districts that are inhabited by a race of dark complexioned men. If it should then appear that the effect of the sun's rays is not to produce a permanent darkness of the skin, and one that is transmitted to the offspring, and that there are no other external causes which seem in any degree likely to effect this change, we are led to search for internal causes, depending on some peculiar state of the constitution generally, or of the surface of the body in particular. On this point, it appears extremely difficult to arrive at a decisive conclusion: any thing that promotes the vigour of the body seems to have a tendency to darken the skin and the hair; while the effects of civilization and refinement have an opposite tendency. Civilization appears, indeed, to be the most permanent cause of a change in the complexion; and many facts are brought to prove the influence of this agent in altering the tinge of the skin. The natives of the South-sea islands, who all appear to have sprung from the same common stock, but are now dispersed through a wide extent of surface, who are prevented from communicating with each other, and exist in very different states of refinement, seem to the author to afford all the data for determining this question. The fact is that the most savage tribes among them are quite black, with woolly hair ; while the more civilized communities are nearly of the same complexion with Europeans, and have long hair, with the same anatomical structure. It is to be observed that these whiter nations live nearer the equator than many of the more black and savage islanders.

Dr. Prichard recapitulates the train of reasoning employed in this part of his work so judiciously, that we shall gratify our readers by giving it in his own words:

It will be proper to recapitulate in this place our inferences concerning the effects of climate and of civilization on the human species.

We endeavoured in the first instance to shew that there is no foundation for the common opinion which supposes the black races of men to have acquired their colour by exposure to the heat of a tropical climate during many ages. On the contrary the fact appears to be fully established, that white races of people migrating to a hot climate, do preserve their native complexion unchanged, and have so preserved it in all the examples of such migration which we know to have happened. And this fact is only an instance of the prevalence of the general law, which has ordained that the offspring

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shall always be constructed according to the natural and primitive constitution of the parents, and therefore shall inherit only their con nate peculiarities and not any of their acquired qualities. It follows that we must direct our inquiry to the connate varieties, and to the causes which influence the parent to produce an offspring deviating in some particulars of its organization from the established character of the stock. What these causes are seems to be a question which must be determined by an extensive comparison of the phænomena of vegetable and animal propagation. It appears that in the vegetable world cultivation is the chief exciting cause of variation. In animals climate certainly lays the foundation of some varieties, but domestication or cultivation is the great principle which every where calls them forth in abundance. In the human species we endeavoured to ascertain what comparative effect these two principles may produce, and first to determine whether climate alone can furnish any consider able variation in tribes of men uncultivated or uncivilized. We com■. pared the appearances of two great races of uncivilized people, each of which is scattered through a great portion of the world, and which taken collectively, constitute nearly all the savage tenants of the globe. It resulted from this comparison, that little effect is produced by the agency of climate alone on savage tribes. Varieties indeed appear more ready to spring up in moderate than in intensely hot climates, but they are not sufficient to produce any considerable change on the race. Civilization however has more extensive powers, and we have examples of the greatest variation in the human complexion produced by it, or at least which can scarcely be referred to any other cause, viz. the appearance of the sanguine constitution in a race generally black. Lastly, it appears that in races which are experiencing the effect of civilization, a temperate climate increases the tendency to the light varieties, and therefore may be the means of promoting and rendering the effect of that important principle more general and more conspicuous.'

The necessary consequence of the principles which have now been laid down is, that the primary inhabitants of the earth were black; and that the progress of nature has been the gradual transmutation from the negro to the European. Several analogical arguments, drawn from the inferior animals, are adduced in proof of this position, which at least tend to render it probable; and various considerations are also brought forwards to shew that the negro form and complexion are better adapted to his savage condition, while that of the European is more suited to the civilized state in which he is placed. Still, however, all these arguments must be considered as merely giving probability to an hypothesis, which must be established by a reference to facts and historical documents. The author, therefore, devotes the latter part of his volume to an investigation of the physical history of man; in which he collects all the historical data that bear on this question, and endeavours to shew how the different races of men are connected with each

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other,

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other, and thus to refer them to one common origin. We shall not attempt to follow him through this long detail; only remarking concerning it, that the general impression produced in our minds is favourable. It is interesting, comprehensive, and candid; and although, on such topics, much must be left to conjecture, and important conclusions are often built on slender foundations, yet Dr. P. seems to have employed the best arguments that the nature of the subject afforded him. His general conclusion from the historical is the same with that which he draws from the physical argument; viz. that all the different tribes of mankind may be traced to one common origin. Even those who should not agree with us in thinking that Dr. Prichard has made out a plausible case must, we apprehend, allow that he defends it with learning and ingenuity, and that he has produced a work of much amusement and information.

ART. III.

Elements of Agricultural Chemistry, in a Course of Lectures for the Board of Agriculture. By Sir Humphry Davy, LL.D. F.R.S. L.&E. M.R.I. &c. 4to. 21. 28. Boards. Longman and Co. 1813,

OF

F the importance of a rational attempt to improve the theory of agriculture, to explain the principles which ought to regulate the practice of it, and to determine how far we are enabled to direct the operations of the vegetable functions, no person can doubt. Even the most unscientific cultivator of the ground will admit that his art requires farther improvement, that his knowlege is still extremely imperfect, that he is ignorant of the causes of many of his actions, and that, when he ventures to reason, the attempt often leads him into error. It will also be granted that considerable light has been thrown on the physiology of vegetables, that many va luable discoveries have been made respecting the connection between this science and chemistry, and that, in various instances, we are able to comprehend the manner in which the vital powers influence inorganic matter. Although in agriculture, as well as in the arts which are intimately connected with the functions of the animal body, successful practice is the ultimate appeal to which all our hypotheses must be referred, yet the experience of ages concurs to prove that practice alone is almost as fruitful in mistakes as mere theory; and mankind are now generally agreed that all expectation of extensive improvement must be founded on a judicious union of the two.

With these impressions on our minds, we entered on the perusal of Sir Humphry Davy's elements with high expectations both of amusement and instruction; and, if in some particulars the work has not fulfilled our expectations, we acknowlege that it contains much important matter, a considerable part of which is now for the first time given to the world.

It is stated in the preface that the author has delivered lectures to the Board of Agriculture for the last ten years, and that these lectures are now published at the request of that body. They are eight in number. The first is entirely devoted to introductory observations and to pointing out the difficulties of the undertaking, the principal objects which he proposes to accomplish, the plan of the course, and the arrangement of his materials. Sir Humphry thus defines or characterizes agricultural chemistry: Agricultural chemistry has for its objects all those changes in the arrangements of matter con nected with the growth and nourishment of plants; the comparative values of their produce as food; the constitution of soils; the manner in which lands are enriched by manure or rendered fertile by the different processes of cultivation.' He then very appropriately illustrates the connection that subsists between agriculture and chemistry, shews how the former is calculated to derive assistance from the latter, and points out several individual instances in which chemical investigations immediately lead to agricultural improvement. The definition given of agricultural chemistry may probably be deemed too comprehensive, since it includes much that strictly belongs to physiology: but, at the same time, we must remember that the two sciences are so intermixed and blended together, that it would be very difficult to draw an accurate line of demarcation between them, or to treat of one without encroaching on the other. The subsequent observations, which occur towards the conclusion of the lecture, will be regarded by our readers as exhibiting a philosophical view of the mutual advantage that results from the judicious combination of theory and practice:

• Information collected after views of distinct enquiry, would ne cessarily be more accurate, and more capable of being connected with the general principles of science; and a few histories of the results of truly philosophical experiments in agricultural chemistry, would be of more value in enlightening and benefitting the farmer, than the greatest possible accumulation of imperfect trials, conducted merely in the empirical spirit. It is no unusual occurrence for persons who argue in favour of practice and experience, to condemn generally all attempts to improve agriculture by philosophical enquiries and chemical methods. That much vague speculation may be found in the

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works