GEOLOGY OF MADEIRA. 43 



Visible on botli sides of the valley. Near the head of U, a 

 short distance IVom the cascade, the red stratum is at the 

 bottom, aiid about 60 feet hic;her it reappears, and again, 

 about 200 feet hii^her, alternating with the gray lava. The 

 upper red lava dips rapidly to the south, and the strata are 

 disposed in the followajg uianiier. 



Ciray lava. 



Lower Red. 



The rock, down which the cascade falls, is also intersected 

 \vith a red stratum of about 3 fe^-t wide, that traverses it, 

 and dips to the westwaid, and is broken off by a broad dyke 

 of gray biva. It appears about 30 feet higher, and dips 

 again to the westward. The substance of the red rock in 

 this place is hard, and it, breaks into a columnar form, 

 being by far the most compact of the red strata I met with 

 in the island. 1 saw this rtd lava also in the island of Tene- 

 riffe, to the eastward of Santa Cruz, as well as in the neigh- 

 bourhood ( f Oiotava. 



1 have I hus endeavoured to give you a slight sketch of The island de- 

 that which appeared to me most deserving of attention in "^ " ' *a\thet 

 the island of Madeira. The short stay 1 was able to make 

 there prevented a more accurate survey of the island; yet I 

 saw enough to induce me to recommend a careful examina- 

 tion of the strata to those who may have more time than I 

 bad to »*pare, and more knowledge to estimate the value of 

 that which was to bt seen. To my mind the most interest- Most interest- 

 ing geological iacts are: 1st, The inteisection of the lava by '"S facts ob' 

 dykes at rightangles with the strata. 2dly, The rapid dips 

 the strata rnake, particljlarly the overlaying of that of the 

 Brazen Head, to the eastward of Funchal, where the blue, 

 gray, and red lavas are rolled up in one mass, and lie in a 

 position as if they had all slipped together from an upper 

 stratum. 3dly, i i;e colum a f rm of t e ava it elf re- 

 posing on, and be ng c er d b, , eds f co ide, ash s, and 

 pumice, which affords a saong argument for the volcanic 



origin 



