over the whole range of forest vegetation throughout both continents. The tabular view of these plants which is given below, will at once show the correspondence and divergence.

From these facts it might be inferred that the aspect of wooded lands, whether mountainous or level, would be very similar; that in the northern regions, 'it compares in every respect with that of high mountain chains. Such an impression is almost universally prevalent among those who are conversant with these laws of the geographical distribution of plants, without having had an opportunity actually to compare such countries. It having been my good fortune, after having been for years familiar with the vegetation of the Alps, to visit the northern regions of this continent within the limits of the temperate zone, I was at once struck with the great difference in the general aspect of their vegetation. Indeed, the picturesque impression is an entirely different one, and nevertheless the above-mentioned laws are correct; but the fact is that the changes of mean annual temperature in this country take place at the rate of about 1° of Fahrenheit for every degree of latitude, or for every sixty miles; or in other words, as we travel north or south, we reach successively every sixty miles, localities the mean annual temperature of which is 1° Fahrenheit lower or higher; while in the Alps we meet, in ascending or descending, the same change of 1° Fahrenheit in mean annual temperature, for every three hundred feet of vertical height; so that we pass within the narrow limits of between six to seven thousand feet, from the vine-clad shores of the lakes of Northern Italy and Switzerland, to the icy fields of snowmountains, whose summits are never adorned by vegetation; a journey which can easily be performed in a single day. Whilst on the other hand from the 40th degree of northern latitude, where the mean annual temperature is nearly the same as that of the foot of the Alps, we find towards the northern pole a diminution of one degree of temperature for every degree of latitude, or for every sixty odd miles; so that we should travel over twenty degrees of latitude, or more than twelve hundred miles from south to north, for instance, from Boston to Hudson's Bay, before passing over the same range of climatic changes as we do in one day in the Alps; thus causing a narrow vertical stripe of Alpine flora to correspond to a broad zone of northern

vegetation stretching over a widely-expanded horizon. So that notwithstanding the correspondence of species, we have in the first case, in the Alps, a rapid succession of highly-diversified vegetation, whilst in the other case, in northern latitudes, we have a monotonous uniformity over extensive tracts of land, although the elements of the picture are the same. But it is a picture seen in a different perspective in one case we have a simple vertical profile, which in the other case is drawn out into disproportionate horizontal dimensions; like the far-reaching shade of a steeple cast under the light of the setting sun, which may change all proportions, and destroy all resemblance between the shade and the object itself, simply because it is so much elongated. Fantastic images presented at various distances before a light falling at various angles, may prepare us to understand these different aspects of the landscape, be it a wooded plain along a gentle slope, or a forest along a more abrupt mountain chain.

There is another feature in the geographical distribution of organized beings which deserves to be particularly noticed, and which contributes to increase the diversity of aspect of vegetation in any given part of the world. There are in all continents remarkable differences between the vegetation of the shores of a continent, east and west, within the same latitude or the same isothermal line. The forests of the Atlantic and Pacific coasts of temperate America are not altogether composed of the same plants; we remark that in the East there will be a tendency in the different families to develop in different proportions, and perhaps with the addition or disappearance of one or two peculiar types; for instance, the walnut family contains several more representatives on the eastern side of the continent than on the western, and they prosper here in latitudes where in Europe there is only one introduced species of that family growing wild. Again, we find Liquidambar on the American side of the Atlantic, which has no representative either on the Pacific coast, or in Europe. This comparison might be traced farther, and we should see the same correlation even among the shrubs.

But these indications will be sufficient for my object, which is to show that, although there is an intimate correlation between climate and vegetation, the temperature and other influences which constitute climate do not reveal the whole amount of causes which produce

these differences, as they are repeated under the same isothermal lines, between the eastern and western shores of the Old World in the same order as along the eastern and western shores of North America; so much so that the northern Chinese and Japanese vegetation coincides very closely with that of the Atlantic States, whilst that of the Pacific coasts of America and that of Europe agree more extensively. This picture would be incomplete did I not institute a farther comparison between the present vegetation of those regions and the fossil plants of modern geological epochs. If we compare, namely, the tertiary fossil plants of Europe with those living on the spot now, we shall be struck with differences of about the same value as those already mentioned between the eastern and western coasts of the continents under the same latitudes. Compare, for instance, a list of the fossil trees and shrubs from Oeningen, with a catalogue of trees and shrubs of the eastern and western coasts, both of Europe, Asia, and North America, and it will be seen that the differences they exhibit scarcely go beyond those shown by these different floræ under the same latitudes. But what is quite extraordinary and unexpected, is the fact that the European fossil plants of that locality resemble more closely the trees and shrubs which grow at present in the eastern parts of North America, than those of any other part of the world; thus allowing us to express correctly the differences already mentioned between the vegetation of the eastern and western coasts of the continents, by saying that the present eastern American flora, and I may add, the fauna also,* and probably also that of Eastern Asia, have a more ancient character than those of Europe and of Western North America. The plants, especially the trees and shrubs growing in our days in this country and in Japan, are, as it were, old-fashioned; they bear the mark of former ages; a peculiarity which agrees with the general aspect of North America, the geological structure of which indicates that this region was a large continent long before extensive tracts of land had been lifted above the level of the sea in any other part of the world.

The extraordinary analogy which exists between the present flora

• The characteristic genera Lagomys, Chelydra and the large Salamanders with permanent gills remind us of the fossils of Oeningen, for the present fauna of Japan, as well as the Liquidambar, Carya, Taxodium, Gleditschia, etc. etc.

and fauna of North America, and the fossils of the miocene period in Europe, would also give a valuable hint with respect to the mean annual temperature of that geological period.

Oeningen, for instance, whose fossils of all classes have perhaps been more fully studied than those of any other locality, could not have enjoyed during that period a tropical or even a sub-tropical climate, such as has often been assigned to it, if we can at all rely upon the indications of its flora, for this is so similar to that of Charleston, South Carolina, that the highest mean annual temperature we can ascribe to the miocene epoch in Central Europe must be reduced to about 60° Fah.; that is to say, we infer from its fossil vegetation that Oeningen had, during the tertiary times, the climate of the warm temperate zone, the climate of Rome, for instance, and not even that of the northern shores of Africa. We are led to this conclusion by the following argument :-The same isothermal line which passes at present through Oeningen at the 47th degree of northern latitude, passes also through Boston, lat. 42°. Supposing now, (as the geolog ical structure of the two continents and the form of their respective outlines at that period seem to indicate,) that the undulations of the isothermal lines which we notice in our days existed already during the tertiary period, or in other words, that the differences of temperature which exist between the western shores of Europe and the eastern shores of North America, were the same at that time as now, we shall obtain the mean annual temperature of that age by adding simply the difference of mean annual temperature which exists between Charleston and Boston, (12° Fah.,) to that of Oeningen, which is 48° Fah., as modern Oeningen agrees almost precisely with Boston, making it 60° Fah.; far from looking to the northern shores of Africa for an analogy, which the different character of the respective vegetations would render still less striking. The mean annual temperature of Oeningen during the tertiary period would not therefore differ more from its present mean, than that of Charleston differs from that of Boston.

This old-fashioned look of the North American forests goes also to show the intimate connection there is all over the globe between the physical condition of any country, and the animals and plants peculiar

to it. But far from supporting the views of those who believe that there is a causal connection between these features of the creation, we must, on the contrary, conclude from the very fact that there are so many special thoughtful adaptations for so long successive periods in their distribution, that those manifold relations could only be introduced, maintained and regulated by the continuous intervention of the Supreme Intelligence, which from the beginning laid out the plan for the whole, and carried it out gradually in successive times.

What is true of plants is also true of animals; we need only remember that it is in North America that Lepidosteus and Percopsis are found; that species of Limulus occur along the Atlantic shores; and that Trigonia and Cestracion live in New Holland along paleozoic rocks.