Grayson.] 266 _ [June 7, 



well opened, but it is doubtless of the same species from which the 

 cultivated cotton has been originally obtained. Wild tomatoes and 

 capsicum are found growing in the woods. 



"The physical and geological structure is strange and peculiar, 

 especially so, as differing from any other formation found upon the 

 coast. 



"The indications and unmistakable evidences we read upon their 

 surface lead us to the conclusion that the materials of which they are 

 composed once lay at the bottom of the sea, and have been raised to 

 their present form, at some period of the earth's history, and perhaps 

 subsequent to the elevation of the adjacent region composing the 

 main land. 



"The stratified formation appears to be horizontal, and but little 

 broken or disturbed, throughout the Island of Maria Madre. The 

 strata are well defined, particularly where there is a precipitous bank 

 or cliff exposing them to view. The composition of these layers is 

 various. The most common is a conglomeration of sea mud and 

 gravel, in which vast quantities of fossil shells and coral are mingled. 

 Some consist entirely of soft sandstone, while in others lime and 

 chalk are found. Large boulders, lying detached and scattered about 

 over the surface, have the appearance of granite, but upon near 

 inspection prove to be solid blocks of coral formation, which, where 

 they are gradually becoming decomposed, are soft and easily broken. 

 Vast masses of fossil shells, cemented compactly together, form in 

 many places ihe upper strata. Many of them appeared identical 

 with fresh shells found upon the shore. 



"I discovered no indications of volcanic phenomena. Pumice 

 stone is found in some localities near the beach, but its rounded and 

 water-worn appearance shows it to have been drifted there by the 

 waves of the ocean. In fact the regularity of the strata and the 

 general physiognomy, especially of the largest island, shows that they 

 probably have not been subject to any remarkable convulsions. 



"The island of Socorro, about two hundred and forty miles west of 

 the Marias, which is about thirty miles in length and fifteen in width, 

 presents a very different aspect. Its formation is entirely volcanic 

 and its strata tilted and thrown into every position, and its high and 

 peaked mountains prove it to have undergone severe convulsions. 



"But the Tres Marias seem to have risen gently and gradually 

 from the sea, nearly in the shape they now present, with the excep- 

 tion of the ravines and creek beds formed by the natural courses of 



