Pacific, as is shown by Lieutenant Maury in his Physical Geography of the Sea, though he makes the rains come down entirely too far to the south in regions known to receive but little.

3. A few words on Florida will show its peculiarities in relation to trees and climate. The trees of Georgia extend for a long distance, some of them continuing as prevailing forms almost to its extremity. But they are gradually replaced by more tropical species, although where the most marked line of distinction exists is not well known. Most of those in the special list have been yet found only on Key West, but the examination of the almost unexplored interior, especially the Everglades, will doubtless extend their range materially. Forty-eight out of seventy-eight species found in it are evergreen, and all but four of these the broad-leaved tropical forms.

Towards the middle of the State are found extensive prairies and treeless tracts, which are evidently connected with the alternation of wet and dry seasons, generally well marked in its climate. Though the wet season is in summer, yet the little interruption of growth by cold at other seasons makes their dryness influential. Its effects will be hereafter more fully alluded to.

4. Now coming to the CAMPESTRIAN PROVINCE we find, as already stated, that no new forms of trees appear, while those found rapidly diminish and disappear towards the west. Thirteen species have not been traced west of its eastern border; about ninety extend pretty far into the Texan and Illinois regions, but only five or six get across the castern limit of the Camanche and Dacotah regions, which, however, receive nine or ten more from the west and north.

The Saskatchewan region, bordering close upon the well-wooded Lacustrian Province, may have a few more eastern species, and possibly more from the west, as there is evidence that it is better watered and approaches in character to the Illinois region.

It will be observed that the southeast and northeast borders of this province form nearly a right angle with each other, and extending east into Michigan cause a wide separation of the Lacustrian and Apalachian provinces. This is one of the most well defined facts in the distribution of trees. A careful examination of the minute land office surveys has shown that the line is exceedingly distinct in Wisconsin and Minnesota, prairies prevailing to the south of it interspersed with oak-openings and groves of deciduous trees along the streams, while to the north pine and spruce forests with tamarack swamps cover the whole country, having the other Canadian trees with them. This is doubtless in great part due to the change in the character of soil and of the underlying rocks, which retain the moisture, while it is completely drained off to the south. Thus we have here a distinct division of the two eastern forest provinces, assisting to determine where it would be eastward were it not disguised by local irregularities of surface.

The cause of the disappearance of trees in the Campestrian Province is, in a word, the deficient and irregular supply of moisture. I need not enter into the proofs of this, but refer to the records of meteorologists. It is true that this does not materially affect agriculture in the more eastern regions; in fact, most crops will succeed better with

less rain than is necessary for most trees to thrive, and in some years there is even a greater supply of rain in the Texan and Illinois regions than eastward. But there are years and series of years of drought, when in their natural condition the forests take fire from the slightest cause and burn over large tracts. This was made even more general by the Indians, but since the white settlement has in great degree ceased and forests have been re-established. In the Apalachian region droughts have never been sufficient to keep trees from extending themselves as soon as a forest might be partially destroyed by fire, and thus the formation of prairies has been prevented. A consideration of the source of the rains will explain why the limit of prairies has its present direction. Coming north from the Gulf they are continually carried more and more eastward by the westerly winds; and as the greater part of the moisture is precipitated before reaching the Ohio river, the Illinois region is deprived for many years of its due share of rains.

The Texan region lying quite west of the line of travel of those Gulf streams has to depend on less abundant sources for its rains. Now, as we go westward the supply rapidly diminishes until in the Camanche and Dacotah regions it is entirely inadequate to the growth of trees as well as of most cultivated products; and in some parts even grass and other herbage entirely disappear over vast tracts. From the great bend of the Missouri north, however, there seems to be an improvement in the country. On the banks of that river, above Fort Union, there is no long interval without trees as there is farther south on nearly all the streams, and on the Saskatchewan there is even less.

The very porous character of the soil and underlying rocks assists much in this aridity of the country, and we therefore find that the line marking the junction of the carboniferous rocks of the Illinois region with the cretaceous and tertiary is a distinct limitation of many trees.

When better known the geological character will help much in defining the physical geography of the surface of this province. In Texas the border of the Llano Estacado coincides with that of the Camanche region for a long distance. It is evidently more the retentiveness of the soil than its mineral composition that affects the growth of trees, for all soils contain more or less of their essential ingredients. Even the saline substances, which are supposed by some to make deserts of portions of the Great Plains, are rather the secondary effects of the climate; for if rains were abundant these salts would become diffused, and in their proper proportions enter into the structure of trees and other plants.

It is certain, however, that even if the fires cease very few trees will ever be made to grow in these two arid regions.

5. Coming now to what I have called the Rocky Mountain province, we find that the relations of climate and forest characteristic both of the Campestrian and Apalachian provinces are repeated, but combined in an entirely new manner.

The high mountain ranges resemble the latter in their regular supply of rain, while near their summits the vegetation of the Athabascan region appears either in identical or allied forms, and still higher,

near the limits of perpetual snow, the Esquimaux vegetation is almost precisely copied. But, on the other hand, the lower plains present every shade of succession, from the continuous forests of the Apalachian, through the rich prairies of the Illinois, to the barren deserts of the Camanche region. All these characteristics occur, however, in comparatively narrow belts surrounding isolated peaks or ranges, and the species of trees met with are nearly all distinct from those of the eastern provinces.

Another distinctive character is in the fact that this province receives its rains from the west, (except, perhaps, some of the most eastern mountain slopes and those of Arizona,) and the supply of moisture is in direct proportion to the vicinity of any region to the Pacific, and the obstacles between it and that reservoir. Thus the Sierra Nevada cuts off almost all the rain from Utah, the little that reaches its eastern part being from local evaporation and what is intercepted by the lofty central ranges from the higher currents of the atmosphere.

It thus happens that no constant elevation and no similar exposure has always the same amount of forest or other vegetation; local circumstances make every range of mountains and every valley differ somewhat from those around it.

But, as a general fact, we find that those regions towards the north are the best supplied with moisture, and therefore best wooded-exactly contrary to the character of those regions which receive their moisture from the Gulf of Mexico.

Near the Mexican boundary we enter the belt of rainless regions described by Lieutenant Maury; and here the supply is indeed precarious, though apparently more adequate to vegetation than in the Utah region.

Although I have enumerated a long list of trees as first appearing on this line, it is in reality, for the most part, a treeless belt. Scattered individuals of numerous species occur, often limited to one narrow locality, as if merely outlines of more extensive forests in Mexico, or of what were once more extensive here, and have been destroyed by drought. Lieutenant Ives found great tracts of some of the more common trees thus standing dry and dead, as if killed within a recent period; but this is not the place to discuss these apparent changes in the climate of the country.

The higher San Francisco and other ranges seem, however, to receive a better supply of moisture from the upper strata of the air, while their more impervious rocks probably retain it, and their cool summits condense around them enough moisture for the leaves of trees. I may remark here, that it would seem as if trees, rising high above the surface of the ground and expanding a vast evaporating surface of leaves to the air, require a greater degree of moisture in the air than herbaceous plants. They cannot, like the herbs of all arid regions, dry up and die down to their roots, to spring again with the wet season; they must retain vitality throughout or die. This constitutes a real physiological distinction between trees and herbs. The shrubs which live in those arid regions, presenting less evaporating surface, and having larger rootstocks in proportion, withstand droughts.

6. The Californian region stands alone, unless combined with the

Peninsula by natural affinities. Its mountains essentially resemble in climate and forest growth the Lacustrian province. Its valleys are like the Illinois and Texan regions, with this difference: that they have periodic dry and wet seasons, occurring at seasons opposite to those of Florida. Connected with this and with the mildness of its winters we again find a large proportion of broad-leaved evergreens, several genera, as the oaks and chestnut, which are deciduous in the east, being nearly all evergreen there. I should have mentioned that the same is the case in Arizona, though there a climate of tropical heat requires no interruption of vegetation.

7. The Oregon region, and those north of it, as far as known, have very peculiar characters as well as points of resemblance to the eastern region. The climate is mild and equable, without excessive heat or cold, the rains abundant, and towards the coast excessive, with but short intervals, scarcely amounting to a dry season. The forests, while mostly composed of the northern forms of Coniferae, have also several broad-leaved evergreen trees and shrubs, which give them almost a tropical aspect. Both in climate and vegetation this western coast resembles much the coast of Europe, species and genera of trees being almost identically represented, and in about the same numbers. On the other hand, a similar analogy exists between the Apalachian forests and those of China.

The marked differences in the character of the various mountains and valleys in these western regions may in future lead to more minute division than I have adopted, but present information does not warrant it now. Species formerly supposed to be limited to a narrow district have unexpectedly been found in others far distant, but of similar natural character, the intervening wide tracts being entirely destitute of them. Many facts go to show that the distribution of trees and forests was once very different, and is even now constantly changing, together with the climate; but as even the possibility of this change is doubted by some, except with such geological convulsions as can upheave mountains and sink continents, we must not be hasty in deciding the question.

It may be objected to what I have said of the connexion between the cold winds and the constant rains of the Apalachian province that they do not coexist in the northwestern regions, which, together, form the CAURINE PROVINCE. But there are other causes which produce the precipitation of rain there. One is the cold northwest seabreeze, which in winter precipitates the moisture brought by the southwest winds; the other is the cold air around the peaks of perpetual snow, which in summer produces at night a downward cold current with the same condensing effect.

Thus the snowy mountains assist to improve the climate, and intercept much of the rain which, more to the north, seems to pass over the lower mountain ranges and to reach the Lacustrian province.

Much more might be said respecting the connexions of forests and climate, but the general and best known facts are presented so as to lay the way for more complete observations. The provinces and regions may be classified in the following manner as to these connexions:

A.-Completely wooded; rains equally distributed and abundant.The Lacustrian and Apalachian.

B.-Partially wooded; rains sometimes deficient.-Florida, Texas, and Illinois regions.

C.-Almost woodless; rains always deficient.-Dacotah, Camanche, and Utah regions.

D.-Plains and valleys unwooded; mountains wooded in proportion to their moisture, which is irregularly distributed, or periodical.-Rocky mountain province, except Utah?

E.-Partially wooded; rains periodical.—Californian region and Mexican province ?

F.-Nearly all densely wooded; rains somewhat periodic, increasing in amount to the north, and with elevation.-Caurian province. From what examination I have been able to give the subject, I conclude that at least fifteen inches of rain during the growing season is essential to the vegetation of trees of all kinds. This, however, must vary with the retentiveness of the soil, the rapidity of evaporation, and the species of tree, some requiring much more than this. We have seen that, with its abundant moisture at all seasons, the Apalachian province has far the greatest number of species of trees, while the Caurian, though with perhaps more rain, unequally distributed, has much fewer. This is, however, connected also with its cooler summers, and, as before remarked, we have in the east a tropical forest with our tropical summers, in spite of arctic winters.

From an accurate determination of the range of trees much interesting information on both climatic and other physical influences is expected to be derived. At the same time the distribution of all other plants and of animals must be studied in order to arrive at a knowledge of that harmonious system which undoubtedly prevails throughout the organic world, however obscured by the accidents of time and of external influences. Among them all we believe that forests will be found one of the most important, and respectfully invite the attention of the reader to its investigation.

LIST OF BIRDS OF NOVA SCOTIA.

Compiled from notes by Lieutenant Blakiston, R. A., and Lieutenant Bland, R. E., made in 1852-1855, by Professor J. R. Willis, of Halifax.

[N. B.-The species with an asterick (*) prefixed are inserted on the authority of Andrew Downs, esq. The nomenclature is that of Audubon's synopsis.]

Bald-headed Eagle, (Haliaeetus leucocephalus.) Resident; not un

common.

Osprey, (Pandion haliatus.) Common along the coast; breeds. *Ice Falcon, (Falco islandicus.) Very rare and only in winter; one instance in ten years.-(A. Downs.)-??? J. R. W.

Pigeon Hawk, (F. columbarius.) Common; breeds.