branner: the stone reefs of brazil. 185 



time member of the committee of the British Association, " appointed 

 for the purpose of inquiring into the rate of erosion of the sea-coasts of 

 England and Wales." ^ So far as his own observations go, Mr. Whitaker 

 tells me that he does not recall a single case of the hardening of beach 

 sands. He gives nie, however, the following interesting unpublished 

 note made by Bauerman, in connection with one of Mr. Whitaker's 

 papers on the Alderley Edge Copper- works, written in 1861 or 1862 : — 



" A curious deposit of a similar character has been noted in Cornwall, at the 

 Perran Mine near St. Agnes. The slow oxidation of small quantities of cop- 

 per-pyrites in the wash heaps of the old works, which rest upon blown sand, 

 produced soluble copper salts which were infiltrated by the rain into the saud 

 below, producing irregular concretionary masses cemented together by green 

 carbonate of copper. Many of the larger modules contained quartz pebbles 

 and snail shells. These sands were worked as copper-ores in the year 1853." 



There must be more or less of the hardening of beach sands, however, 

 on almost all shores during the summer months where the shallow 

 waters are warmed by the sun. But unless this hardening passes a cer- 

 tain amount, it can never produce perceptible effects, because storm- 

 waves during the rest of the year break up this incipient consolidation. 

 In the tropics this sort of deposits is more common. 



'' At many points on a reef where evaporation takes place, there is a 

 deposition of amorphous carbonate of lime cementing the whole reef 

 materials into a compact conglomerate-like rock." ^ These consolidated 

 beaches, however, appear to be local rather than widespread, even in the 

 tropics.* 



If the preceding facts were the only ones concerned in the inorganic 

 deposition of lime carbonate, we might reasonably expect to find the 



1 Report of the British Assoc. Adv. Sci. for 1885, p. 402-442. 



W. Wliitaker, Chronological list of works on the coast changes and shore depos- 

 its of England and Wales. Kept. Brit. Assoc, 1885, p. 442-465. 



W. Whitaker, Second chronological Ust, etc. Kept. Brit. Assoc, 1895, p. 388- 

 402. 



2 Murray. Nature. Feb., 1889, XXXIX., p. 427. 



' For other examples of the consolidation of beach sand by sea-water, see " A 

 voyage of discovery into the South Sea," etc., by Otto von Kotzebue. III., p. 332. 

 London, 1821. 



James D. Dana, Corals and coral islands, 152. New York, 1800. Anier. Journ. 

 Sci., 1885, CXXX., p. 103. 



James D. Dana, Points in the geological history of the islands Maui, and Oaliu. 

 Amer. Journ. Sci., 3d ser., XXXVII. 1889, p. 80. 



A. Agassiz, A visit to the Great Barrier Keef of Australia. Bull. Mas. Conip. 

 Zoul., XXVII., No. 4, p. 108, and Plate IV. Cambridge. 1808. 



