THESOURCE OF THE NILE. 221 



north-weft monfoon which repels it, and keeps it in there, 

 every rock on the Arabian fliore becomes an Jlaud, and e^e- 

 ry two or three iflands become a harbour. 



Upon the ends of the principal of thefe harbours large 

 heaps of ftones have been piled up, to ferve as fignals, or 

 marks, how to enter ; and it is in thefe that the large vef- 

 fels from Cairo to Jidda, equal in fize to our 74 gun mips, 

 (but from the cifterns of mafon-work built within for hold- 

 ing water, I fuppofe double their weight) after navigating 

 their portion of the channel in the day, come fafely and 

 quietly to, at four o'clock in the afternoon, and in thefe 

 little harbours pafs the night, to fail into the channel again, 

 next morning at fun-rife. 



Therefore, though in the track of my voyage to Tor, I 

 am feen running from the weft fide of Jibbel Zcit a W. N. 

 W. courfe (for I had no place for a compafs) into the har- 

 bour of Tor, I do not mean to do fo bad a fervice to huma- 

 nity as to perfuade large mips to follow my track. There 

 are two ways of inftrufting men ufefully, in things abfo- 

 lutely unknown to them. The firft is, to teach them what 

 they can do fafely. The next is, to teach them what they 

 cannot do at all, or, warranted by a preffing occafion, attempt 

 with more or lefs danger, which ftiould be explained and 

 placed before their eyes, for without this laft no man knows 

 the extent of his own powers. With this view, I will venture, 

 without fear of contradiction, to fay, that my courfe from 

 CofTeir, or even from Jibbel Sibergct, to Tor, is impoffible to 

 a great fhip. My voyage, painful, full of care, and danger- 

 ous as it was, is not to be accounted a furety for the lives of 

 thoufands. It may be regarded as a foundation for furveys 

 hereafter to be made by perfons more capable, and better 



protected ; 



