•28 THE GEOLOGICAL STRUCTURE, ETC. 



their supplies from the Fayette Sands. Owing, however, to the 

 large quantity of impurities, chiefly common salt, the water of 

 these wells was found to be quite unsuitable for domestic use, 

 though it was employed to a large extent for manufacturing 

 purposes. With the view of ascertaining whether a more 

 wholesome supply could be obtained from greater depths, the 

 municipal authorities of Galveston decided to bore to a depth of 

 3,000ft., at about which depth it was expected that the water in 

 the Trinity Sands would be tapped. The section in the deep 

 well gives an idea of the thickness of the strata pierced, as well 

 as the amount of their dip. The well passed through oloft. of 

 recent and coastal clays, and about 2,000ft. of Tertiary beds. 

 From the known elevation and distance of the outcrop of the 

 different series, the dip has been calculated, and turns out to be 

 .about 18ft. per mile towards the sea. When the Galveston well 

 reached 3,070ft., the authorities concluded that the experiment 

 had gone far enough ; as, though the water obtained was 

 brackish, it was much less so than any of the other shallow 

 wells in the city. (Plate II, fig. 1). 



Wells have been sunk on the mainland near Galveston, and 

 these furnish a decidedly better quality of water than those on 

 the island. Further inland, at the town of Houston, there are 

 over 100 wells, whose depths vary from lloft. to 564ft. The 

 water contams no impurity in the form of common salt. 



The strata of the Gulf Border region have been proved to 

 be continuous southwards into that portion of the Eepublic of 

 Mexico which fringes the shores of the Gulf, to a point about 

 20degs. north of the equator. According to the researches of 

 the Mexican geologists, representatives of both the Lower and 

 Upper Cretaceous have been recognised, the latter being 

 unusually well developed. I have been unable to get access to 

 the maps and publications of the Mexican Geological Survey, 

 which deal with the formations and district in question ; hence 

 the information is much more meagre than I could wish. 



Having described in some detail the coastal areas, the 

 ■ central portion of the continent known as the Great Interior. 

 Region now remains to be dealt with. 



" The eastern boundary of the great Cretaceous area of the 

 •" interior may be designated as corresponding to the western 



