120 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



had a false dip on the steep front varying from 34° to 37°. An un- 

 usually steep beach up and down which waves were running at the mouth 

 of Rio Sapucahy had a slope of 11°. 



Liais states, however, that these reef beds are sometimes vertical. 

 This is true, but in no case has the writer seen a reef rock in place in a 

 vertical position. The hard reef rocks rest upon soft sands ; it fre- 

 quently happens that the reef is undermined by cui-rents, and huge 

 blocks of stone falling in the soft sands are left tipped about in various 

 positions and even standing on end. 



3. Reef rocks above high tide. — Whether rock above high tide can 

 be accepted as evidence of elevation depends on how the rock was 

 formed. M. Liais speaks of the reef rock as having been formed beneath 

 the sea.-^ If that were the case, the reasoning might pass, but it is doubt- 

 ful, to say the least. The toppling over of a large mass in the manner 

 just referred to sometimes lifts one end out of the water and beyond the 

 reach of high tide. Besides such cases there are instances of the harden- 

 ing of beach sands beyond the reach of the tides. This hardening may 

 be caused either by spray being blown by the wind several metres 

 higher than the tides rise, or it may be produced by rain water dissolving 

 the lime from the upper layers of sand and depositing it again lower 

 down. There are many excellent illustrations of this hardening of sands 

 far above tide on the island of Fernando de Noronha ^ and at other places 

 in the world, though the writer does not remember to have seen any on 

 the Brazilian mainland. 



The case "of the recession of the sea cited by Capanema occurs in the 

 State of Ceara, He says of it : " In Ceara the elevation has been con- 

 siderable near Aquiraz in a place where the sea has receded ten fathoms 

 in thirty years, and to this the inhabitants cannot apply their favorite 

 explanation — the accumulation of sand — for the poles have not been 

 covered."^ The italics are mine. He does not state whether or not 

 the land uncovered is hard rock or soft sands and clays, and in order 

 to judge of the meaning of such phenomena it would be necessary to 



1 L'Espace Celeste, p. 545, 548. 



2 J. C. Branner. Geology of Fernando de Noronha. Amer. Joiirn. Sci., 1889, 

 XXXVI., p. 160-161. 



J. C. Branner. The aeolian sandstones of Fernando de Noronha. Amer. Journ. 

 Sci.. 1890, XXXIX., p. 247-257. 



H. B. Woodward. The Geology of England and Wales, ed. 2, 1887, p. 546-7, 550-1. 



T. McK. Hughes. Ancient beach and boulders near Braunton and Croyde, 

 Quar. Journ. Geol. Soc, 1887, XLIII., p. 657-670. 



3 Op. cit., p. cxxxvii. 



