Crosby.] 126 [November 1, 



the western part of the island, where the erosion is less rapid 

 than farther east, they are the predominant formation ; and are 

 well preserved on the summits of the highest hills. Mr. Alexan- 

 der Agassiz states that the hills about Havanna and Matanzas, 

 which reach a height of over twelve hundred feet, are entirely 

 composed of reef-limestone. 



Five miles west of Baracoa, and thirty miles from Cape Maysi, 

 rises a singularly bold and interesting mountain, called by the 

 Spaniards El Yunque (The Anvil). 



It is a very prominent landmark, known to all sailors in these 

 seas, and indicated upon nearly all maps and charts of eastern 

 Cuba, the altitude, when given, ranging from 2500 to 3000 feet. 



It stands about four miles, in a direct line, from the sea, with 

 only slight undulation of the ground intervening, so that the eye 

 takes in the entire altitude at a single glance. This probably 

 accounts for the fact, of which I have no doubt, that the alti- 

 tude of the mountain has been very generally and very greatly 

 over-estimated. I have visited the summit twice ; and my closely 

 accordant observations with the aneroid and plane-table show 

 that the true altitude cannot vary from 1800 feet. The ground- 

 plan of the mountain is distinctly rectangular ; and at the sum- 

 mit it is about three-fourths of a mile long and one-third as broad, 

 with the longer axis parallel with the coast. The slopes, except 

 at two or three points, where only, ascent is possible, are vertical 

 or nearly so for the first 300 to 600 feet below the summit. 



The form of the mountain points very clearly to its origin ; and 

 before making the ascent I felt that it must be simply the last 

 remnant of an ancient coral-reef, differing from those already de- 

 scribed chiefly in its great altitude. This theory was confirmed by 

 observation. The base of the mountain, up to a height of about 

 800 feet, is composed mainly of the ancient eruptive rocks of the 

 island with some slates ; while upon this foundation rests not less 

 than one thousand feet of limestone, forming the entire upper 

 half of the mountain. The limestone is crystalline, and I ob- 

 served in it no traces of corals or other organisms. In fact, it is 

 very unlike the modern reef-rock ; and, taken by itself, there is 

 little evidence that it had a similar origin. But when, as its 

 form warrants, we regard El Yunque as the highest and oldest 



