292 ALEXANDER AGASSIZ 



able to get an excellent impression of the elevated ter- 

 races that form such an important feature of this part 

 of the coast of Cuba. On the way north from the east 

 end of Cuba, after touching at Inagua, the yacht an- 

 chored in Hogsty Eeef . This is a horseshoe-shaped line 

 of breakers with an opening at the western end into an 

 enclosed lagoon, and forms an atoll about five miles 

 by three, which, with the exception of two little cays, 

 one on each side of the entrance, composed of broken 

 fragments of coral, has not yet had time to make any 

 land. The line of coral reef over which the sea breaks, 

 except in one or two exposed spots, has at least a foot 

 to a foot and a half of water over it even at low tide, 

 but as the reef was some one thousand yards wide, the 

 interior of the lagoon was quite calm, though encircled 

 by bands of white combers piled up by the heavy roll 

 of the trade winds pounding on the flats.' 



Agassiz, now for the first time anchored in a lagoon, 

 was much impressed by the novelty and strangeness of 

 riding quietly in three fathoms of water, surrounded by 

 lines of huge breakers, with nine hundred fathoms a 

 short distance beyond, and forty-five miles to the near- 

 est land. 



Here he passed three days, surveying, sounding, 

 and investigating ; and reached the conclusion that the 

 atoll was probably formed by a growth of coral on a 

 bank previously formed by the wearing away of a series 

 of small seolian hills. The existence of the lagoon he 

 attributed to the mechanical action of the surf rushing 

 over the reef. For he thought the mass of water poured 

 over the rim would be a sufficient scouring force in time 

 to hollow out the lagoon within, where, moreover, the 

 conditions were less favorable to a luxuriant growth of 



