THE WEST INDIAN WATERS. 



339 



direction of tlie American officers attached to the Coast Survey. Howell, Pour- 

 tales, Alexander Agassiz, Bartlett, Sigsbee, Baird, and others, have studied this 

 maritime region from every point of view, and their labours are still continued in 

 constantly-increasing detail. JN'ot only have careful soundings been everywhere 

 taken, but the most sensitive instruments have been used to determine the varying 

 temperature at different depths, the course of the upper and lower currents, their 

 saline properties, thermometric deviations, and so forth. Special attention has been 

 paid to the marine fauna down to the darkest recesses of the abyss, and thus have 



Fig. 157. — Gtjlf op Mexico. 



Scale 1 : 18,500,000. 



to 250 

 Fathoms. 



250 to 500 

 Fathoms. 



Depths. 



500 to 1,000 

 Fathoms. 



1,000 to 1,750 

 Fathoms. 



300 Miles. 



1,750 Fathoms 

 and upwards. 



been made many startling discoveries, which open marvellous vistas into the past 

 evolution of life on the globe. 



The outer basin between Cuba, the Bahamas, and Florida, through which the 

 Gulf Stream escapes northwards, is comparatively shallow, being almost entirely 

 occupied by banks, with intervening channels 200 to 300 fathoms deep. South- 

 eastwards, however, the deeper Old Bahama Channel skirts the north side of Cuba 

 to a great distance, in several places presenting cavities of over 1,000 fathoms. 

 At the entrance of the New Bahama Channel, due north of Havana, the soundings 

 have revealed an abyss of 850 fathoms. 



But the circular inner basin of the Gulf is much deeper, the whole of the 



