20 cook's first voyage OCT. 



red, some of them three or four feet in length, which, 

 upon being touched, sting like a nettle, but with much 

 more force. On the top of the bladder is a mem- 

 brane which is used as a sail, and turned so as to 

 receive the wind which way soever it blows : this 

 membrane is marked in fine pink-coloured veins, and 

 the animal is in every respect an object exquisitely 

 curious and beautiful. 



We also took several of the shell-fishes, or testa- 

 ceous animals, which are always found floating upon 

 the water, particularly the Helta: Janthina and Vio- 

 lacea ; they are about the size of a snail, and are 

 supported upon the surface of the water by a small 

 cluster of bubbles, which are filled with air, and 

 consist of a tenacious slimy substance that will not 

 easily part with its contents ; the animal is oviparous, 

 and these bubbles serve also as a nidus for its eggs. It 

 is probable that it never goes down to the bottom, 

 nor willingly approaches any shore ; for the shell is 

 exceedingly brittle, and that of few fresh water 

 snails is so thin : every shell contains about a tea- 

 spoonful of liquor, which it easily discharges upon 

 being touched, and which is of the most beautiful 

 red purple that can be conceived. It dies linen 

 cloth, and it may perhaps be worth enquiry, as the 

 shell is certainly found in the Mediterranean, whether 

 it be not the Purpura of the ancients. 



On the 8th, in latitude 8° 25' North, longitude 

 22° 4/ West, we found a current setting to the south- 

 ward, which the next day in latitude 7° 58', longitude 

 22° 13', shifted to the N. N. W. | W., at the rate of 

 one mile and a furlong an hour. The variation here, 

 by the mean of several azimuths, appeared to be 

 8° 39' W. 



On the 10th, Mr. Banks shot the black-toed gull, 

 not yet described according to Linnseus's system ; 

 he gave it the name of Larus crepidatus : it is re- 

 markable that the dung of this bird is of a lively red, 

 somewhat like that of the liquor procured from the 



