390 



gists to notice even any portions of the skull, and to direct 

 their attention, when possible, to these remains. 



Dr. Samuel Kneeland, Jr., presented specimens of the 

 rock and calcareous substance, which form the reef at Per- 

 nambuco, Brazil, and gave an account of the reef. 



This reef is one of the greatest curiosities of its kind, being 

 quite straight for several miles along the coast, parallel to, and a 

 httle distance from, the shore ; it is from thirty to sixty yards 

 wide, perfectly level, covered with water only at high tide ; the 

 surface is deeply channelled in all directions, giving refuge to 

 myriads of small fishes, crabs, and echini, specimens of which he 

 presented to the Society several years since. 



It is composed of obscurely stratified hard sandstone ; the surf 

 beats heavily against the outer side, leaving a smooth and safe 

 harbor on the inside of the reef, though with strong currents. 

 This reef is so regular in its width, and so level, that it is difficult 

 to believe it to be the work of Nature ; it looks like the work of 

 a skilful engineer. 



In 1836, Dr. Darwin in his " Researches in Geology and Natu- 

 ral History," says, — " With respect to the origin of the reef, I 

 believe a bar composed of sand and pebbles formerly existed 

 beneath the water, when the low land, on which the town now 

 stands, vvas occupied by a large bay ; and that this bar was first 

 consolidated, and then elevated." He gives another slightly dif- 

 ferent-explanation, which he thinks equally probable, namely, 

 '* that a long spit of sand had its central part consolidated, and 

 then, by a slight change in the set of currents, the loose matter 

 removed, so that the hard nucleus alone was left." 



Notwithstanding the heavy beating of the ocean against it, 

 there is no record of the least decay. Dr. Darwin attributes its 

 protection " to a layer of calcareous matter, formed by the suc- 

 cessive growth of several kinds of organic bodies, chiefly serpulse, 

 balani, and nuUipor^e, but no true corals ;" he considers it a pro- 

 cess analogous to the formation of peat, and, like the latter sub- 

 stance, preserving from degradation the matter on which it rests. 



