134: THE ATLANTIC. [chap. ill. 



The specimens from great depths are much larger than those 

 from shallow water, and are much more delicate and fragile. 

 The largest specimens ]3rocured by Count Pourtales measured 

 one centim. in diameter ; our largest specimens were three 

 centims. in diameter, and those from deep water in the North 

 Pacific averaged two centims. The specimens from the dia- 

 tom ooze bottom, though large, were evidently growing under 

 circumstances unfavorable to the formation of a corallum, the 

 bottom being almost entirely siliceous, and only containing a 

 trace of lime ; their coralla were so fragile that they broke 

 with the sliglitest touch. From an examination of the long 

 series of this coral obtained by us, there seems to be no doubt 

 of their belonging to one species, and certain series obtained 

 near Bermudas and the West Indies are certainly identical with 

 the Fungla symmetrica of Pourtales, although some of the 

 larger specimens seem to show close affinities with the Lopho- 

 seriuEe. 



On Tuesday, the 14th of October, we sighted the island of 

 Tristan, distant fifty miles to the south-south-west. 



The Tristan d'Acunha group, so named from the Portuguese 

 navigator who discovered it early in the sixteenth century, lies 

 in mid-ocean, about thirteen hundred miles south of St. Helena 

 and fifteen hundred west of the Cape of Good Hope, nearly on 

 a line between the Cape of Good Hope and Cape Horn ; it is 

 thus probably the most isolated and remote of all the abodes of 

 men. The group consists of the larger island of Tristan and 

 two smaller islands — Inaccessible, about eighteen miles south- 

 west from Tristan, and Nightingale Island, twenty miles south 

 of the main island. Tristan only is permanently inhabited ; the 

 other two are visited from time to time by sealers. We hear 

 little of Tristan d'Acunha until near the close of last century ; 

 but even before that time it appears to have been the occa- 

 sional resort of American sealers. Captain Patten, of the sliip 

 Industry^ from Philadelphia, arrived there in August, 1790, and 



