SPANISH TOPOGRAPHICAL EXPRESSIONS. 65 



The parallelism is a fact now better understood than the natural laws which effected it. The 

 linear extension of the axis may be supposed to be the result of electro-magnetic forces combined 

 with the action of tidal currents, together with other causes, such as isothermal, isoclinic, and 

 isodynamic currents. We offer the following explanation, founded on our own observations : 

 After the first formation of the dykes and reefs composing the sierras, the result of vol- 

 canic forces, acted upon by electro-magnetism, sedimentary strata commenced to be formed. 

 The igneous forces, however, at this time prevailed, and as a consequence, the strata of that era 

 exhibit a crystalline character. By the increase of volcanic detritus and sedimentary material, 

 the igneous ejections were confined to certain fissures only, whilst the action of aqueous forces 

 became more general. The crust thereby becoming more and more firm and overlaid, the 

 molten masses had to seek other outlets, determined, perhaps, by the character of the sedi- 

 mentary rocks through which they led. To the stratification, lamination, and cleavage of the 

 sedimentary rocks, as determining the subsequent direction of these volcanic forces, we may 

 ascribe the formation of the catenary mountain ranges and dykes, and the cellular system of 

 their intermediate bases. 



The mountain ranges are mostly one-sided upheavals of metamorphic strata ; the dykes^ on 

 the contrary, are essentially volcanic eruptions. The two classes of mountains are seen in a 

 diversified combination of volcanic, plutonic, and aqueous or sedimentary rocks ; syenitic and 

 granitic lavas; trachyte and trap still exhibiting clear traces of lamination, cleavage, and strati- 

 fication ; granite, gneiss, syenitic, and various transition slates. How far this view may agree 

 with the observed geognostical data, the special survey will show. 



Before entering on this subject, we propose some remarks on a few Spanish terms which define 

 their objects with a precision that could hardly be otherwise arrived at except by much circum- 

 locution. These words are — 



Cordillera, which means a long, continuous range of mountains, composed of several ridges, 

 sometimes united by cross spurs, and intersected by passes or narrow valleys. The essential 

 characteristic of this word is, that it means a mountain composed of two or more ranges forming 

 one orographical body, just as several strings twisted together make a cord. The words cord 

 and Cordillera are formed from the same stem. 



Sierra, a saw, indicates a mountain range with a serrated crest. A cross section of either 

 sierra or cordillera is very small compared with its longitudinal axis. 



Cuchilla. — This signifies a branch or outrunner of a sierra, which it usually resembles in its 

 physiographical character. Its sharply edged crest, in all probability, suggests its name — 

 cuchilla meaning knife. 



Picacho means a sharp peak rising conspicuously above a surrounding mass of mountains ; its 

 height bears the same proportion to its width that the longitudinal axis of a sierra does to its 

 cross section. 



Puerto — a gate, or gap, and also a post. In its topographical application, a pass over or 

 through a mountain range. 



Canon implies a defile or mountain pass without any outlets on either side. 



Loma is a long mountain, or ridge of hills, with a somewhat smooth and flat surface. Lomita 

 is the diminutive form of the same word. ^ 



Mesa is a table-land, table-mountain, or a flat-top ridge. Menillu is the diminutive. 

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