368 
INCLINATION OF THE STBATA. 
In taking a general view of the geological constitufirai 
ol a eham of mountains, we may distinguish five eletnents of 
direction too often confounded in worlis of geognosy and 
physical geography. These elements are: — 
1. The longitudinal axis of the wliole chain. 
2. Ihe line that divides the waters (divortia aquarum). 
3. The hue of ridges or elevation passing along the maxima 
of height. 
4. J he line that separates two contiguous formations into 
horizontal sections. 
5. The line that follows the fissures of stratification. 
This distinction is the more necessary, there existing pro- 
bably no chain on the globe that furnishes a perfect parallel- 
ism of all these directing lines. In the Pyrenees, for instance, 
1, 2, 3, do not coincide, but 4 and 5 (that is, the different 
formations which come to light successively, and the direc- 
tion of the strata) are obviously parallel to 1, or to the 
direction of the whole chain. AV e find so often in the most 
distant parts of the globe, a perfect parallelism between 1 
and 5, that it may be supposed that the causes which deter- 
mine the direction of the axis (the angle under which that 
axis cuts the meridian), are generally linked with causes that 
deteriniue the direction and inclination of the strata. This 
direction of the strata is independent of the line of the 
formations, or their visible limits at tbe surface of the soil; 
the lines 4 and 5 sometimes cross each other, even when one 
of them coincides with 1, or with the direction of the longi- 
tudinal axis of tlie whole chain. The relief of a country 
cannot be precisely explained on a map, nor can the most 
erroneous opinions on the locality and superposition of the 
strata be avoided, if we do not apprehended with clearness 
t lie relatioD of the directing lines just mentioned. 
In that part of South America to wiiich this memoir prin- 
cipally relates, and which is bounded by the Amazon on 
the south, and on the west by the meridian of the Snowy 
Mountains (Sierra Nevada) of Merida, the different bands or 
zones of formations (4) are sensibly parallel withthe loimitu- 
dinal axis (1) of the chains of mountains, basins, or interposed 
plains. It may be said in general th.at the granitic zone 
(including under that denomination the rocks of granite 
gneiss, and mica-slate) follows the direction of the Cordillera’ 
