Crosby.] 124 [November 1, 



Some of the results named above are better established than 

 others; and all deserve scrutiny and re-examination in the 

 field. It is largely with the hope of exciting local observers to 

 this work that the above outline of a method of investigation 

 has been written. Many facts of a kind that can be well learned 

 from thorough observation within a comparatively small field 

 must be collected ; and the results from these many small fields 

 must be collated for the Triassic district that the fields make up. 

 When this is done, there is some chance that the cause as well as 

 the facts of the monoclinals may be discovered. The most impor- 

 tant questions for local observation are : the identification of the 

 source of the conglomerate pebbles ; the proof of intrusive or 

 overflow origin for all the trap sheets ; and the discovery of faults 

 by the repetition of similar series of strata. 



ON THE ELEVATED CORAL REEFS OF CUBA. 



BY W. O. CROSBY. 



One of the most striking, and, to the northern eye, one of the 

 most novel, features presented by the island of Cuba, when viewed 

 from the sea or from salient portions of the coast, are the broad, 

 level and vertical-walled terraces or shelves of rock which rest 

 against the jagged mountains of the interior and form the shore 

 around almost the entire island. I have observed these terraces 

 lying at various levels from twenty up to nearly two thousand 

 feet above the sea. Even when seen from a distance, and for the 

 first time, the observer feels satisfied that they must be composed 

 of horizontal beds of either some sedimentary rock or of basalt. 



Landing on the first terrace, which, for hundreds of miles, has 

 a sensibly uniform altitude of about thirty feet, and is unbroken, 

 save where rivers have cut through it to reach the sea, the most 

 casual observation shows that the indescribably jagged and ragged 

 rock is a limestone, and largely made up of several kinds of 

 modern-looking corals. In other words, the terrace is a fringing 

 coral-reef that has been lifted above the level of the sea; ajid 

 looking from the perpendicular front of this ancient reef we can 



