322 The American Geolo^^ist. November, 1904 
localities has Dr. Branncr been able to find s'liai reefs men- 
tioned, viz., about the shores of Asia Minor, to .some extent 
about Greece and about Sicily, and upon the shores of the 
Red sea. These bear some resemblance to the stone reefs of 
Brazil and have been produced by the recent hardening of 
beach sands by the deposition of carbonate of lime. 
Consequently the inves'tigation resolved itself into the 
question : Why is this hardening of beaches by lime appar- 
ently confined to the beaches of the Levant and those of the 
northeast coast of Brazil? 
The sands were microscopically and chemically examin- 
ed. They are mainly quartz, which is often abundantly sup- 
plied with inclusions. In these inclusions are sometimes two 
or more bubbles, and the inclusions are then believed to be of 
glass. From this circumstance the quartz is referred to a 
molten magma having a deep-seated origin and is supposed to 
have been derived from granite or some rock formed under 
similar conditions of depth and pressure. It is, however, as 
appears to the writer, more compatible with the granitic tex- 
ture to exclude glass from deep-seated structures, and to assign 
it to surface volcanic rocks. Indeed the presence of glass in 
any rock implies sudden cooling from a molten condition and 
that could hardly take place except at or very near the sur- 
face. If the glass be correctly identified, it is evidence hence 
of surface volcanic rock, as the source of the quartz containing 
it. Chemicallv the cemented Sands .contain over 63 per cent 
of silica, over 2 per cent of carbonate of lime, about 5 per 
cent of carbonate of magnesia and very small amounts of soda," 
potash, iron and alumina. 
The author considers and dismisses the following partial 
sources of the material of the cement: 
1. Dis'solved from rain-water, or spray from the beach 
sands themselves ; that is, carried from the upper layers of 
the sand and deposited in the lower ones. 
2. Depoisited from the ocean water after having been 
derived (through agency of carbon-dioxide) from calcareous 
organic bodies in the sea. 
3. Brought down frc^m the land bv streams. 
4. Dissolved from calcareous l)each sknds by fresh (or 
acid) water o^f streams entering behind them, and redeposited 
while ])assing seaward through these s^inds. 
