produced by these features in modifying either a gust of wind or the set of a current is enough in the lapse of ages to cause such an accumulation of materials in particular spots as will occasion these phenomena. Thus it becomes important, with reference to the mere geographical outline of a country liable to such modifications, independently of pure geological causes, to ascertain and describe all those features by which such important changes may be effected.

But independently of these direct changes, the physical outlines and features of a country exercise a great influence in modifying its meteorological character, as well as the social, political, and commercial position of its inhabitants. In vain should we look for much commerce amongst a people whose country possessed no navigable rivers; in such a case the sea-coast alone, if easily accessible, might offer a few points where trade or barter could be carried on. A sea beset with coral reefs and rocky islets will offer to the observation of the naturalist a series of phenomena entirely different from those offered by one free from these obstacles to navigation. Again, the climate of a country will in many respects be regulated by its physical character. The nature of the soil and the form of country will mainly determine the amount and character of its vegetation. The retentive qualities of clay forming the basis of a low plain will support a rank and marshy vegetation very different from that which will prevail in a hilly or mountainous district: all these various qualities of vegetation will in their degrees exercise considerable influence on the climate, particularly when taken in conjunction with its greater or less proximity to the equator. The climate, again, cannot fail to influence the habits, social developement, and civilization of the inhabitants, as well as the Natural History of each particular country. Thus we trace a close connection between its physical configuration and those questions which have to be discussed in considering, in its most extended sense, the geographical features of different districts.

In order to bring together the various points to which the foregoing observations refer, they may be arranged under the following heads, which will be found to embrace most, if not all, of the important features of the subject, and respecting each of which it will be necessary to say a few words.

1. Form of country; whether consisting of hills, valleys, or plains.

2. Mountain ranges; their direction, height, slope, and spurs; their woods and forests.

3. Rivers; their sources, obstacles, size, and mouths; their beds and banks, affluents and confluents.

4. Springs; whether hot or cold or mineral; their localities, temperature, &c.

5. Lakes, marshes, lagoons; how surrounded, and when supplied with water.

6. Coast-line, sand dunes, harbours; nature of shore, whether sandy, rocky, or muddy.

7. Oceans; their depth and currents; islands, rocks, shoals, &c.

1. Form of country; whether consisting of hills, valleys, or plains. The physical configuration of a country is the first object which engages the attention of a traveller on entering a new locality, and this may be described in general terms as flat, undulating, hilly, or mountainous; or the country may be divided into districts, to each of which one of the above terms of configuration may be applied. Each of these, however, is susceptible of great modification. A flat country may be a sandy desert, a rich alluvial plain, or a marshy, boggy tract; it may be well watered by rivers. and streams, or arid and parched up; it may contain numerous lakes; it may be barren, or wooded, or cultivated as arable or grass land; each of these features may be of importance, or at least of interest: nor must the nature of its soil be omitted, whether sand, or marl, or clay, as the appearance of the country will often depend greatly on this circumstance. In some cases the plain may stand at a

higher level than the surrounding country. Such elevated plains are usually called uplands, or plateaux (Hoch ebene, in German). Other important characteristics of a plain are its form and extent, and the natural features by which it is bounded, whether by mountains, rivers, or seas; how many miles wide, and how many long; whether extending parallel with the coast, or running up between hills into the interior.

Many of these characteristics, it will be observed, belong equally to the other forms which constitute the character of the district. An undulating country may be barren, wooded, or cultivated; it may be arid, or watered by streams, &c. The undulations may be abrupt, or only gently swelling, and this may be in a great measure owing to the nature of the subsoil, whether it consists of gravel, or sand, or rock. A country of this description is easily described, but a hilly country, on the other hand, is more complicated. Not only is the term vague and uncertain, but other features have to be considered in reference to it. Neither hills nor mountains can exist without valleys, respecting which also there are many points of interest deserving notice, which will be farther alluded to hereafter. Then, again, the hills themselves may be of various forms and characters: Do they extend in long parallel chains or ranges, or are they detached and isolated? Do these ranges of hills radiate or converge? Do they rise abruptly or gradually from the low country? and how are they wooded? What do the rocks which constitute their nucleus and their flanks consist of? If possible, it is desirable to ascertain their height, which, in the absence of complicated instruments and barometers, may be obtained approximatively by marking the exact point at which pure fresh water boils. It is a well-known fact that water, when heated in an open vessel, boils at a lower temperature in proportion as we ascend to a higher elevation above the level of the sea. It is hardly necessary to observe that the same accuracy cannot be obtained as with the barometer, but much may be done with the help of well-graduated

thermometers. The apparatus for this purpose is very simple, and not liable to the same derangements as the barometer. On a limited scale, and where the means of comparison are at hand, the aneroid barometer may be used for this purpose with great advantage. Another simple method of measuring the height of mountains within sight of the sea is by taking the angle of depression of the sea-horizon, from which the height of the station may be calculated by a very simple formula.

2. Mountain ranges.-The most important features in the configuration of a country are the mountain ranges by which it is traversed. The exact point of distinction between a hill and a mountain is difficult to describe; in some cases it will be purely comparative, in others it will depend on the general character of the country, and in some it will be arbitrary. But in all cases it will be desirable to endeavour to ascertain the height of the principal points, the direction of the main ranges or chains, and whether they are parallel or not. The ridges may be serrated (jagged like a saw), or smooth and even, and the summits themselves will be either pointed, or domeshaped, or flat. Is the mountain insulated or not? and if so, is it conical and sloping on all sides to the surrounding plains, or does it consist of a detached ridge? Many of these points will be found to depend on the geological formation of the country, and, as we have already observed, this branch of our subject is very closely connected with geological science. Ascertain also how far the mountain tops are covered with perpetual snow, and how far down their sides snow lies during the whole or any considerable portion of the year, and how far glaciers, if they exist, can be traced down the valleys, as well as the extent of lateral or terminal moraines. Is there any marked difference in the slope on the one side or on the other? Does vegetation abound more on one side than on the other? e. g. in Asia Minor it has been observed that the mountain ranges which extend from east to west (and this is their principal direction) are covered on their northern flanks with

uxuriant vegetation and magnificent forests; while the southern flanks, exposed to the rays of an almost tropical sun, are void of vegetation, barren, and generally rocky. This superior vegetation on the northern flanks is probably owing to the less rapid melting of the snows or drying up of rain there than on the southern flanks; consequently, south of the equator, the phenomena would be reversed. It may also sometimes be owing to the fogs and vapours driven up by the sea breezes, condensed on coming in contact with a colder body, or attracted and retained by the hills themselves. But here, again, we enter on the province of the botanist; and yet the geographer should inquire how far vegetation extends up the mountain side, and what are the changes which it undergoes. How far is it influenced by the change of soil, or the abundance or absence of springs?* Nor is our information respecting a mountain chain complete, unless we know the length to which it extends, and the breadth of country which it

covers.

Valleys are a necessary complement to mountain masses, and there are many peculiarities connected with them well deserving observation. Are the sides precipitous or sloping? are they wide or narrow? well watered or arid? wooded or barren? Do the rocky sides correspond with each other in their salient and re-entering angles? How far do they extend into the bosom of the mountains? and how are the subordinate valleys connected with the principal one? There is also another peculiarity of valleys not to be lost sight of. There are some which convey to the traveller the impression that he is passing through a mountainous or hilly country, so steep, rugged, and lofty are the hills by which he is surrounded. It is only on reaching their summit that he becomes aware that the country through which he has been passing is an extensive plain, or table-land, intersected by deep chasms and valleys,

*The illustrious Humboldt, the most distinguished of living travellers, is a fine example of the importance of a knowledge of botany to the true geographer.