CANARY ISLANDS. 87 



certained that in caves in the south of France, human re- 

 mains have been found along with bones of quadrupeds 

 the species of which are now extinct. The examination of 

 caves and caverns has been particularly recommended to 

 travellers, as not only being intimately connected with the 

 early history of man, and his condition in a low state of 

 civilization, even at the present day, but also with the 

 geological history of our species, and that of several of the 

 more powerful and interesting species of quadrupeds. 



Although a considerable quantity of rain falls here at 

 certain seasons, these islands afford comparatively but few 

 springs. This may be accounted for, however, by exam- 

 ining the nature of the rocks. When two formations come 

 together, the lower one dense and compact, and its upper 

 surface above the level of the neighboring country, and 

 the upper formation soft and porous, springs will occur 

 abundantly around the line of junction of the two forma- 

 tions. In this case, the rain filtrates through the porous 

 formation, and progresses downward until it is arrested by 

 the surface of the dense formation, where it accumulates, 

 and either remains stationary, or finds an opening at the 

 surface, and issues in the form of springs. On the con- 

 trary, if the porous formation extended below the level of 

 the surrounding country, the percolating water would 

 descend so far that it could not find an issue. This dis- 

 closes a very important fact relating to the geology of 

 Teneriffe. For I have not observed in any part of the 

 island, where a spring took its first issue from the earth 

 below 3,000 feet above the level of the ocean, which proves 

 that there exists a formation of dense and compact rocks 

 below that height. 



Springs of mineral waters occur in many parts of the 

 island, the most important of which I mentioned in a for- 

 mer part of this work.* 



Botany of Teneriffe. — Strictly speaking, the island 

 of Teneriffe, in its present state, exhibits but three zones 

 of vegetation. They occur one above the other, and 

 occupy, on the steep declivity of the Peak, its whole per- 



* Vide pp. 57 et 59. 



