« PreviousContinue »
unviolated, and that he represents the eldest branch of the 'far-famed Noachida.'
If we have done any justice to Mr Williams's two essays, we must have excited in our readers a wish warmly cherished by ourselves, that he should fulfil his promise of a larger work on the Geography of Ancient Asia. In executing such a work, his arrangement will naturally be somewhat more methodical, and the digressions, in which he is apt to indulge, will become less numerous. His style, preserving all its strength and freedom, will perhaps more rarely approach the verge of incorrectness. Of the ardour with which he will accumulate knowledge, and the ingenuity with which he will apply it, no doubt can be entertained. There is but one thing that causes us any apprehension. Having addressed the present treatises to Xenophon the Athenian, and Alexander the Macedonian, how is he to rise on the scale of dedication, for the more extensive and elaborate performance? We see nothing left for him unless it be to imitate the example of that grammarian, who composed a volume on Orthoepy, and inscribed it to the Universe.
ART. III.-Fauna Boreali-Americana; or the Zoology of the Northern Parts of British America. By JOHN RICHARDSON, M.D. F.R.S. F.L.S. Part First; containing the Quadrupeds. 4to. London: 1829.
A KNOWLEDGE of the various phenomena presented by the different groups of animals and plants, in accordance with the latitude, the longitude, and the altitude of their position, constitutes the science of physical geography, as applied to organized beings, and forms one of the most interesting and important branches of natural history. When we take an extended survey of the geographical distribution of animals and plants, we find that they are generally disposed over the earth's surface in bands or parallel zones, corresponding, in a great measure, with the peculiarities of temperature and climate which are appropriate to the nature of each. When the temperature of a particular latitude becomes colder, as on mountains or highly elevated plains, or warmer, as on plains by the sea-shore or in low lying sheltered valleys, we find, in the former case, that the species approximate in their nature and characters to those of a more southern, in the latter, to those of a more northern parallel. In regard to the vegetable kingdom, this intimate relation between the species and the temperature was long since ably
illustrated by Tournefort, in his observations on Mount Lebanon. At the base of that mountain, he gathered the productions peculiar to Asia; after these occurred species characteristic of the Italian fields; as he continued to ascend, those of France presented themselves; at a still greater elevation, a Flora, analogous to that of Sweden, was observable; and, among the cold and barren peaks, a botanist might have supposed himself on the summits of the Dophrian Alps. Each zone of the mountain had, in fact, a temperature corresponding to that of the country in which its race of plants most naturally flourished, or where they had what may be called their centre of dominion.
Viewed under a similar aspect, each hemisphere of the earth has been regarded as an immense mountain, of which the equator forms the basis, and the north and south poles the respective summits; and if the general surface were less unequal,—that is to say, presented scarcely any highly elevated plains, or lofty alpine chains, which necessarily derange or alter the direction of the isothermal lines,-then the temperature of countries would bear a much more exact relation to their distance from the equator, and the geographical distribution of plants and animals might be illustrated simply by parallel lines of greater or less extent.*
In the study of zoological geography, there are, however, many minor circumstances to be taken into consideration, which frequently change or counterbalance the more usual results, and consequently derange such calculations as might not unreasonably be formed upon a knowledge of latitudinal and longitudinal position, and of the height of a country above the level of the sea. The nature of the soil and surface, the different degrees of dryness and humidity, and the consequent character of the climate and vegetation, the comparative extent of land
* It is much to be desired that some well-informed zoologist should reconstruct the map prefixed to Zimmerman's Specimen Zoologiæ Geographica Quadrupedum (Leyden, 1777). Though highly meritorious for the period of its publication, it has long been inadequate to represent the actual state of our knowledge. The learned author published a second edition of his map, corrected in relation to the geographical discoveries of Cook; and he has given an explanation of that revised edition in the third volume of his Zoologia Geographica-a work in the German language. Perhaps a better model, as admitting of clearer views and more ample details, would be found in Schouw's excellent Plantegeographisk Atlas (Copenhagen, 1824); where a separate map of the world is given to illustrate the distribution of each of the great natural families of the vegetable kingdom.
and water, the extent and continuity of forests, marshes, and sandy deserts, the direction of mountain ranges, the courses of rivers, the existence of waterfalls, and the form and position of lakes; these and several other circumstances must be taken into consideration, and will be found materially to affect the distribution of animal life over the surface of the earth. The insular position of a country also greatly influences its zoological features, more especially if that country is in the course of rapid improvement or alteration under the hand of man. The draining of fens and marshes, the reclaiming and fencing of commons and other wastes, the clearing of forest lands, the banking of rivers, and the general progress of commerce, agriculture, and inland navigation, consequent on a great increase of population, become by degrees so influential on the local character and physical constitution of a country, that all the larger, and especially the fiercer wild animals are, in the first place, hemmed in and restricted within narrow bounds, and finally altogether extirpated. It is thus that the beaver no longer establishes its republican dwellings on the banks of the Rhone or the Danube,that the bear, the wild boar, and the wolf, cannot now be numbered among the denizens of the British forests,—and that even the hart and hind have scarcely wherewithal to screen themselves from the sultry noontide, amid the scanty remnants of our old ancestral woods.' Indeed, the lion himself, the king of beasts, which in ancient times as an inhabitant of Thrace and Macedonia, must have shaken the hoar-frost from his shaggy mane, has now withdrawn to the distant countries of the East, or the burning deserts of Africa.
The geographical distribution of animals presents a wide field for speculation, although the modes by which that distribution has been effected will probably remain for ever concealed from human knowledge. Their gradual extension by natural means, from a single centre of creation, scarcely falls within the sphere of credibility; and thus the creation of various groups of species over different points of the earth's surface, and in accordance with the climate and physical character of different countries; or the removal and dispersion, by supernatural agency, of the greater proportion of existing species from an original centre, seem the two points, one or other of which remains to be illustrated by whoever is curious in such bewildering speculations. Many legitimate sources, however, of the highest interest, spring on the nearer side of that mysterious bourne which separates our probable knowledge of things, as they exist in their now established relations, from our possible knowledge of the same, or analogous things, as they existed in former times, and in a
different order of relation. It is for the naturalist and the physical geographer assiduously to collect an ample, accurate, and extended series of facts, with a view to exemplify the real and characteristic localities of the species which constitute the animal kingdom-not established upon vague and superficial resemblances, but on the actual knowledge of identical formsand, by comparing and combining these determinate observations, to deduce the laws in accordance with which species and genera are now disposed over the surface of the earth.*
* One of the most important of those preliminary enquiries which are essential to a proper comprehension of zoological geography, consists of the investigation and ascertainment (at least approximately) of the limits which nature has assigned to the variation in the specific characters of animals, and the establishment of fixed and determinate principles, by reference to which it may be discovered whether certain distinctions were sufficient to constitute a specific difference, or were merely the result of climate, or of some peculiar or accidental combination of circumstances. We find, for example, that the golden plover of Europe (Charadrius pluvialis) is described and figured as an American species by Alexander Wilson (American Ornithology, vol. vii. p. 71). Asia, Africa, and New Holland also produce a species, which is so nearly identical, that the individuals from these countries are chiefly distinguishable from those of the first-named regions by the pale hair-brown colour of the inferior coverts of their wings. A certain portion of the commissure of the bill is yellow, and on account of that character, it has been distinguished by Wagler by the specific name of xanthocheilus (Systema Avium); and it is figured under that same designation, as distinct from the golden plover, by Sir William Jardine and Mr Selby (Illustrations of Ornithology, part 6, plate 85). The common magpie of Europe (Corvus pica), and that of the northern parts of North America (Corvus Hudsonius), have been classed as distinct species, in consequence of a still slighter disparity in their plumage (Appendix to Captain Franklin's First Journey, p. 672). So, also, the hooded blackcap (Tinto Negro de Capello), of the island of Madeira, is by some observers regarded as identical with the European species (Curruca atricapilla). If it is identical, how does it happen that a peculiar variety should be confined to the island of Madeira? If it is not identical, it is equally singular that a species, so closely allied both in aspect and manners to the European species, should not have been observed in any continental country. One of the chief difficulties, then, in tracing the distribution of widely-extended species, arises from the uncertainty under which naturalists labour, from the want of a positive and assured test by which to ascertain whether a certain character should be regarded as expressive of specific distinction, or ought rather to be ranked as within the legitimate range of individual variation; whether, in short, such forms of animal life as
It was the opinion of Pennant, that all the animals of America were derived from the north-eastern quarter of Asia, to which they had previously made their way from Mount Ararat, and that the two continents were at one period united as far southwards as the Aleutian Islands, 'in a climate not more rigorous than that which several animals might very well endure, and 'yet afterwards proceed gradually to the extreme of heat.'* This view of the matter does certainly not agree with the coexistences which we now perceive as fixedly established between certain forms of animal life, and the physical characters of countries; neither does it coincide with a multiplicity of special facts with which it ought at least to be in some measure reconcilable.
How does it happen that the tiger has never travelled beyond the continent and islands of Asia, while the sloth has reached South America, and the ornithorhynchus New Holland? Why are the pampas of the New World inhabited by quadrupeds entirely different from the species which occur in the plains of Tar
appear to be repeated over most of the great continents of the earth, should be regarded as specifically the same, or merely as analogous to, or representative of each other. Where we have acquired a knowledge of the habits and economy of a species, and of the individuals of that species, wheresoever found, and if these are uniformly the same under different and far-removed localities, then a trivial distinction in plumage should be regarded as insufficient to constitute a specific difference between them; but when we find the individuals from one country or continent characterised and distinguished by some peculiarity in their instinctive habits, or modes of life, as well as by a cognizable difference of aspect, we are then authorized to infer that they are specifically distinct, and are entitled to rank them accordingly.
We have entered into these apparently trifling details, because we are aware that some modern writers deny that any species is widely distributed, and maintain that every great continent is characterised by organized beings, which form as it were a system in themselves; and that such as appear to be identical with these in other regions are merely a repetition of somewhat analogous forms, and may be detected and described by certain permanent specific characters, independent of colour, or other unessential attributes. This is probably an extreme view of the case; but it is well that it has been brought forward, in as far as it cannot be proved to be either true or false, without leading to a much more accurate comparison of species than has hitherto prevailed; and without precision in these matters, the subject of zoological geography will remain in many respects 'a vast expansion, given over to night and darkness.'
*Introduction to the Arctic Zoology, p. 277.