PRESTER JOHN. 51^ 
aspect of the continent, it was inferred, incorrect- 
ly indeed, yet not unplausibly, that an empire, 
which stretched so far inward from the eastern 
coast, must approximate to the western ; and that, 
by penetrating deep on that side, they could 
scarcely fail at length to reach its frontier. For 
this reason, whenever an expedition was sent out 
to any part of the coast, the first instruction given 
was, to inquire diligently if the inhabitants knew 
any thing of the monarch in question. Every op- 
portunity was also to be embraced, of penetrating 
into the interior ; and, on hearing the name of 
any sovereign, an embassy was to be sent to ascer- 
tain, if he either was Prester John, or could throw 
any light as to where that personage might be 
found. 
So long as the naval career of the* Portuguese 
extended along the shores of the Sahara, and they 
saw nothing before them but a *^ wild expanse of 
lifeless sand and sky," no temptation was felt to 
form a permanent settlement. After passing Cape 
Blanco, however, the coast began to improve ; and 
when they came to the fertile shores of the Sene- 
gal and Gambia, and saw ivory and gold brought 
down in considerable quantities from the interior, 
these regions began to excite the ambition of set- 
tlement and of conquest. The undertaking, how- 
ever, was beyond the force of any expedition that 
had yet sailed from Portugal. Nunez Tristao, in 
