MINERALOGY. 



39-3 



Gtognojy. 21. Law mountain groups are from 600 to 3000 feet 

 ^-y-.^ high. These are the most numerous. The Schwarz- 

 Wald or Black Forest, the mountains between Mora- 

 via and Bohemia, the Thuringer-Wald, &c. belong to 

 this class. 



Mountain groups, in regard to the breadth of 

 their base, are divided into mastiie and imgith groups. 



In miuive mountain groups, the length and breadth 

 f the base are nearly alike. The Swiss and Tyrolian 

 Alps, and the Hartz, are of this kind. 



In the longiik mountain group, the length of the 

 base is very considerable in comparison of the breadth. 

 Of this kind are the Riesengebirge, Erzgebirge, &c. 

 The greater number of groups have this shape. 



23. Mountain groups, in regard to the form of the 

 mountain* of which they are composed, are divided 

 into common, conical, and alpine groups. 



In the common mountain group, the individual 

 mountains of which the chains are composed are sin- 

 gly aggregated, and are joined nearly to their sum- 

 mit-. 



In the conical mountain group, the individual moun- 

 tains of which the chains are composed, are also singly 

 aggregated, but not joined together higher up than 

 the declivity ; so that they appear conical. 



In the alpine mountain group, the mountain chains 

 are composed, not of single mountains joined together, 

 but of groups of pyramidal-shaped mountains, in which 

 groups a large pyramidal mountain has arranged 

 around it a number of smaller mountains of the same 

 figure. 



_'t. Mountain groups, in regard to their connection, 

 are either isolated, or several are joined together, form- 

 ing a chain of mountain groups. A chain of moun- 

 tain groups extend* from the Alps of Switzerland to 

 Servia and Bulgaria : a similar range is farmed by the 

 Fichtelgebirge, which is connected with the Carpa- 

 thians by the Alpine land or mountain group* of 

 the Erzgebirge, Riesenbirge, Silesian and Moravian 

 groups. 



Dncrlptioo ** ?!*"**> * we n * ve already mentioned, form the 



flew land, principal constituent part of lom land ; yet there fre- 



' quently occurs in it flat hilly land, more rarely low and 



isolated groups ; and the hills are often isolated, and 



at a considerable distance from each other. 



The plains of the low land are characterised by par- 

 ticular hollows or concavities, which are denominated 

 river valley*, or freer counet. In these there are to be 

 distinguished the bed of ike river, and the holm or 

 hough land : Further, there are to be observed tin 

 high and l>m bank of the river, and the ravine* or 

 small valleys that traverse the high bank, and termi- 

 nate 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- 

 extendcd lakes. Numerous instance* 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 ground-, which can scarcely be entitled to the 

 name of hills. They often extend for many mile-. 

 They are denominated by German geognosts Land- 

 hohen, when they are nearly of equal length and 

 breadth ; and Landruchen, when they have a length- 

 ened form. 



Hiiinlinldt, in his valuable book of travels, gives an 

 interesting account of the great plains of South Ame- 

 rica, which we shall here lay before our readers. 



Hir 

 JBBBJSJb 



Land- 



In the Mesa de Paja, in the 9th degree of South lati- Geognosy, 

 tude, says Humboldt, we entered the basin of the Llanos, S "V"' 

 The sun was almost at the zenith ; the earth, wherever it s "" th Ame " 

 appeared, sterile and destitute of vegetation, was nt 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 incessantly 

 arose, driven on by the small currents of air that glide 

 only over the surface of the ground, and are occasion, 

 eel by the difference of temperature, which the naked 

 sand and the spots covered with herbs acquire. These 

 sand minds 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 particles of sand striking against the bulb of the 

 thermometer. All around us, die plains seemed to 

 ascend towards the sky, and that vast and profound 

 solitude appeared to our eyes like an ocean covered 

 with sea weeds. According to the unequal mass o 

 vapours diffused through the atmosphere, and the va- 

 riable decrement in the temperature of the different 

 strata of the atmosphere, the horizon in some parts 

 was clear and distinct ; in other parts it appeared un- 

 dulating, sinuous, and as if striped. The e-irth was 

 there confounded with the sky. Through the dry 

 fog and strata of vapour, the trunks of palm-tret * 

 were seen from afar. Stripped of their foliage, and 

 their verdant summits, these trunks appeared like 

 mast* of a ship discovered at the hnri/.on. 



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 

 p*e across the zenith, and announces the approach 

 of the rainy season, sometime* cast its shadow on tin- 

 savannah. I know not whether the first aspect of the 

 llano* excite less astonishment than that ot the chain 

 of the Andes. Mountainous countries, whatever may. 

 be the highest elevation of the highest summits, have 

 an analogous physiognomy ; but we accustom ourselve* 

 with difficulty to the view of the llanos ot V< m/.uel 

 and Casanary, to that of the I'amnat of I'.n. i, .- .\yres 

 and of Chaco, which recal to the mind incessantly, 

 and during journeys of twenty or thirty days, the 

 smooth surface of the ocean. I had seen the plains or Eurojwtn 

 llanos of La Mancha in Spain, and the heath lands pUini. 

 that extend from the extremity of Jutland, through 

 I.uneburg and Westphalia, to Belgium. These last 

 are real steppes, of which man, during several ages, has 

 been able to subject only small portions to cultiva- 

 tion ; but the plains of the west and north of Europe 

 present a feeble image of the immense llanos of South 

 America. It is in the south-cast of our Continent, in 

 Hungary, between the Danube and the Tin i-., : in 

 Russia, between the IUry sthenes, and the Don, and 

 the Wolga, tlwt we find thoe 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 

 frontiers of (iermony, between Freiburg and Oldin- 

 burg, strike the imagination of the traveller by the 

 constant display of the mirage, or extraordinary refrac- 

 tions ; but their greatest extent is more to the 

 between (.'zegled, 1 ' and Tittel, which has 



only two outlet*, one near Gran and \Vaitzcn; tho 

 other between Belgrade and Widdin. 



The different parts of the world have been supposed 

 to be characterised by saying, that Europe has its heath 

 land*, Asia it* itcppct, Africa its dttertt, and America. 



