Mr. H. J. Carter on the Colouring Matter of the Red Sea. 185 



yellowish ; but the filaments, under the microscope, were faintly 

 green. 



Of the questions proposed by Montagne (op. cit. p. 355), the 

 second calls for more information on the size of the bundles. 

 This has been supplied above, so far as my observation extends. 



The third question calls for information respecting the pre- 

 sence of Trichodesmium in the Sea of Oman, &c, as bearing upon 

 the origin of the name "Erythraean Sea/' applied by Herodotus 

 to all the seas washing the shores of Arabia. 



I have already stated that I saw the scum in the Gulf of Aden, 

 also that Mr. Latimer Clark had seen it in the Sea of Oman ; 

 and the following extract from the late Dr. Buist's observa- 

 tions on the " Luminous and Coloured Appearances in the Sea " 

 (Proceedings of the Bombay Geographical Society for 1855, 

 p. 120) will show that it exists in the upper part of the Indian 

 Ocean. The account from which this is taken was communi- 

 cated to Dr. Buist by Dr. Haines, as witnessed on board the 

 ' Maria Soames/ in lat. 21° N. and long. 42° E., and it stands 

 thus : — 



" In May 1 840, when one-third across from Aden to Bombay, 

 the aspect of the sea suddenly changed upon us, and at once 

 seemed as if oil had been poured upon its surface. It was still 

 as a mill-pond, and of a brownish, soapy hue. The water, on 

 being examined, was' full of little fibrils, like horsehair cut 

 across, in lengths of the tenth of an inch or so. A wine-glass 

 full of it contained hundreds of them .... We sailed through 

 them for about five hours ; so that they probably extended over 

 a surface of 500 miles." 



The occurrence, then, of Trichodesmium Ehrenbergii in the 

 Bed Sea, the Gulf of Aden, the Indian Ocean, and the Sea of 

 Oman is so far substantiated; and as the yellow colour in all 

 instances probably passes into red, we have apparently the ex- 

 planation of the whole of these seas having been called by the 

 Greeks " Erythraean/ 5 I have not, however, heard whether it 

 has been seen in the Persian Gulf. 



Further, we learn from M. Dareste's memoir (op. cit. p. 208) 

 that Joao de Castro, in July 1841, when off Cape Fartak, which 

 is about the middle of the south-east coast of Arabia, found the 

 sea so red that it appeared as if it had been coloured with bul- 

 locks' blood. 



In my own experience of the Sea of Oman and the whole 

 shore-sea of the south-east coast of Arabia from Muscat to Aden, 

 where, under its survey, I passed all the months of the years 

 1844-45 and of 1845-46, with the exception of those of the 

 stormy monsoon, viz. June, July, August, and September, the 

 presence of the scum above described never, to my knowledge, 



Ann. % Mag. N. Hist. Ser. 3. Vol. xi. 13 



