356 Prof. Hnrtt on the Brazilian Sandstone Reefs. [June, 



If a beach be growing rapidly, or if it is being rapidly worn 

 away, solidification cannot take place, because it is only over a 

 stationary shore, that is neither receiving new accumulations of 

 sand nor parting with its old, that enough time is granted for the 

 accomplishment of this result. Therefore, consolidated beaches 

 must be the exception and not the rule on the Brazilian coast, 

 where the shore is undergoing much change nearly everywhere, 

 and as sandstone reefs seem to be confined to that single country, 

 it must be that there alone are the proper conditions attained for 

 their formation. The hardening appears to extend from the outer 

 side of the beach inwards, and from below upwards, as new reefs 

 usually lie on the lower and outer part of the beach ; the younger 

 reefs are also softer in texture than the older, more-finished ones. 



It is probable that many of the ordinary Brazilian beaches are 

 solidified below the surface, but until something happens to 

 uncover them, it is impossible to determine the fact. Reefs in 

 process of formation are to be seen on the coasts of both Per- 

 nambuco and Rahia, and at Porto Seguro ; in the latter province, 

 there is a double reef, the outer one being the wreck of an unfin- 

 ished structure, the innsr still underfjoinjr solidification. , 



Prof Hartt was led to believe, from his earlier studies of the 

 Brazilian stone reefs, that a slight elevation of the land was 

 necessary to account for their present position ; but his later 

 studies proved to him that such an hypothesis was wholly 

 uncalled for, and that none of the reefs reach above high tide 

 level, or at the most above the level to which a beach is saturated 

 with water at high tide. 



Statements have been published that a certain amount of 

 upheaval must have occurred to produce the supposed strong 

 seaward dip of the laminae of the sandstone ; but nowhere, 

 excepting on edges where blocks have been undermined and 

 tilted up, is the inclination greater than might obtain on a sand- 

 beach. To suppose an upheaval to have effected these narrow 

 lines of reef, tilting the strata evenly in one direction, and no part 

 of the neighboring coast, is a geological absurdity. The reefs 

 follow the general trend of the shore, and are more or less 

 curved, but generally straighter than the beaches immediately 

 back of them. 



Having shown that the curious reef at Pernambuco, which for 

 many years was a complete puzzle to explorers, has been formed 

 through the agency of very simple forces, in part working upon 



