BRANNER : THE STONE REEFS OF BRAZIL. 247 



the islanfl has shown that the reef follows the subraerf,'ed, out-cropping edges 

 of a series of heavy beds of sandstone, which, at times, bring up on the shore 

 in the form of rocky points. On this solid base the reef appears to have been 

 built, and where, finally, at the south, the sandstone leaves the sea and lies 

 upon the beach, the coral reef ceases to exist. 



" The reef is slightly zigzag in its course, and both edges are very jagged, 

 deeply indented and bordered by projecting or outlying ma-sses ; but so irregu- 

 lar in every part that it would be quite useless for us to try and describe it 

 accurately. At the northern end it is generally elevated on the outer side and 

 low and level on the inner. The higher portion varies greatly in width and 

 height, and is never flattened on top ; it rises rapidly, often abruptly, from the 

 water, but descends more gradually on the inner side to a level of about one 

 foot above ordinary low tide. From here there extends inward a very flat 

 surface, which is generally quite broad but may narrow down or even nearly 

 disappear. Almost everywhere along the inner edge, but more commonly at 

 the ends of the reef and about the openings through it, we find many outlying 

 masses which are often partly continuous with the low, inner surface, but more 

 frequently quite detached. They attain all heights up to that of the lower 

 surface, but never reach above it ; the average depth of water around them is 

 between three and four feet. The outliers on the outside of the reef are merely 

 low, ragged, angular projections from the reef itself, and are never much ex- 

 posed, even at low tide. 



" Between the two divisions of the reef, the elevated outer portion and the flat 

 inner one, there is the most marked contrast. While the latter has been com- 

 pletely smoothed and rounded off, so that scarcely any angles remain upon it, 

 the former retains all the possible roughness that could be brought together on 

 80 narrow an area. The entire raised mass of rock is full of holes of every imag- 

 inable size and shape, the margins of which are always acutely angulated. Every 

 little surface that is not pointed in itself is surmounted by a large and strong 

 barnacle with sharply-edged valves, and large clusters of digitate prcyections 

 stand lip at frequent intervals. This combination of surface is a very uninvit- 

 ing one to look upon, but it is far less pleasant to climb over it or walk along 

 its outer part. The outer slope is by f;xr the most irregular, as the waves, aided 

 by an army of sea-urchins, have broken into it and hollowed out thousands of 

 ragged holes, which, lying concealed beneath the seaweeds, might lead to many 

 accidents were the reefs more frequented. 



" The outer portion of the reef is of a dark and rather rich brown color when 

 wet by the waves, but nevertheless has quite a dead appearance. Examining 

 carefully this brown rock, it is seen to consist generally of an accumulation of 

 very small worm tubes, closely packed together and forming a very hanl maiy<. 

 The surface of the low inner level is of a much lighter color, a rather faded 

 brown, and looks even more lifeless than the part we have been describing; no 

 barnacles or other larger animals grow upon it. 



" What forms of life occur about the reef? On the outer side, reaching to a 

 height of a foot or slightly more above onlinary low tide, is a luxuriant growth 



