25 Plains, as oat- have mentioned, form the principal constituent part of low land ; yet there fre quently occurs in it flat hilly land, more rarely low and isolated groups ; ztiet are hills are often isolated, and at a considerable distance from each other.
The plains of the low laud are characterized by par ticular hollows or concavities, which are denominated river valleys, or river courses. In these there are to be distinguished the bed of the river, and the holm or haugh land : Further, there are to be observed the high and low bank of the river, and the ravines or small valleys that traverse the high bank, and terminate in the low bank.
There is still another kind of hollow to be observed in low land ; it is that formed by shallow and wide extended lakes. Numerous instances of this are to be observed in the great European low land. The Marc Brandenburg affords many instances of these latter. We further observe, that the plains of the low land are not perfectly level, but are frequently marked with rising grounds, which can scarcely be entitled to the name of hills. They often extend for many miles. They are denominated by German geognosts LandMiien, when they are nearly of equal length and breadth ; and Land drikken, when they have a lengthened form.
Humboldt, in his valuable book of travels, gives an interesting account of the great plains of South America, which we shall here lay before our readers.
In the Mesa de Paja, in the 9th degree of South lati tude, says Humboldt, we entered the basin of the Llanos. The sun was almost at the zenith ; the earth, wherever it appeared, sterile and destitute of vegetation, was at the temperature of 48° or 50° centigrade. Not a breath of air was felt at the height we were on the mules ; yet, in the midst of this apparent calm, whirls of dust incessant ly arose, driven on by the small currents of air that glide only over the surface of the ground, and are occasioned by the difference of temperature, which the naked sand and the spots covered with herbs acquire. These sand winds augment the suffocating heat of the air. Every grain of quartz, hotter than the surrounding air, radiates heat in every direction; and it. is difficult to observe the temperature of the atmosphere, without these par ticles of sand striking against the bulb of the thermome ter. All around us, the plains seemed to ascend to wards the sky, and that vast and profound solitude appeared to our eyes like an ocean coveted with sea weeds. According to the unequal mass of vapours dif
fused through the atmosphere, and the variable decre ment in the temperature of the different strata of the atmosphere, the horizon in some parts was clear and distinct ; in other parts it appeared undulating, sinuous, and as if striped. The earth was there confounded with the sky. Through the dry fog and strata of vapour, the trunks of palm-trees were seen from afar. Stripped of their foliage, and their verdant summits, these trunks appeared like masts of a ship discovered at the horizon.
There is something awful, but sad and gloomy, in the uniform aspect of these steppes. Every thing seems motionless; scarcely does a small cloud, as it passes across the zenith, and announces the approach of the rainy season, sometimes cast its shadow on the savannah. I know not whether the first aspect of the Ilanos excite less astonishment than that of the chain of the Andes. Mountainous countries, whatever may be the highest elevation of the highest summits, have an analogous physiogononly ; but we accustom ourselves with diffi cult) to the view, of the lianas of Venezuela and Casa nary, to that of the Pampas of Buenos•Ayres and of Chaco, which meal to the mind incessantly, and during journeys of twenty or thirty da) s, the smooth surface of the ocean. I had seen the plains or Banos of La Mancha in Spam. and the heath-lands mat extend from the ex tremity of Jutland, through Lunebilrg and Westphalia, to Belgium. These last are real steppes, of which man, during several ages, has been able to subject only small portions to cultivation; but the plains of the west and north of Europe present a feeble image of the immense Ilanos of South America. It is in the south-east of our Continent, in Hungary, between the Danube and the Theiss ; in Russia, between the Borysthenes, and the Don, and the \Volga, that we find those vast pastures, which seem to have been levelled by a long abode of the waters, and terminate the horizon on every side. The plains of Hungary, when I traversed them, on the fron tiers of Germany, between Presburg and Oldinburg, strike the imagination of the traveller by the constant display of the mirage, or extraordinary refractions ; but their greatest extent is more to the east, between Cze gled, Debreczen, and Tittel, which has only two outlets, one near Grau and Waitzen ; the other between Belgrade and \Viddin.