Editorial Coimiiciif. 323 
5. Possible inllucncc of cliniaU-. 
While all these sources of the calcareous cementation of 
tlie Brazilian beaches are admittecl as contributory to the re- 
sult, they do not, either sing-ly or combined, answer the de- 
mand, because they are not exceptionally local as the beaches 
are, birt are worUl-wide in their operation and would produce 
universal cementation of oceanic beaches. 
The author finds that calcareous deposition from oceanic 
water is in proportion to its density. He reproduces' a por- 
tion of a chart taken from the Challenger reports, (vol. i) 
showing the areas of densest sen waters over the globe. The 
r\Iediterranean and the Red sea are densest, and aside from 
those areas the cast coast of Brazil and the central parts of 
the Atlantic ocean are repres'ented as approaching nearer to 
them than any other oceanic waters. The westward moving 
tropical current is rendered more dense by evaporation in 
traversing the Atlantic from the African shores, and by the 
time it reaches Brazil it is ready to part with some of its min- 
eral solutions. The latitudes in which this current impinges 
on South America are coincident with those of the Brazilian 
stone reefs. Hence the author finally concludes: 
"The cementing material of the Brazilian stone reefs is 
chiefly lime carbonate. 
The hardening of beach sands may lie produced in the 
following ways : 
1. By carbonated rain water dissolving out the lime 
carbonate in the upper portion of the calcareous sands and 
depositing it in the lower portions. 
2. By the escape of carbon-dioxide from the sea water 
when the surf breaks upon the beaches. 
3. By the escape of carbon-dioxide from sea water where 
where it is warmed by the tropical sun. 
4. ?>y the submarnie cscajie of carbon-dioxide from 
about volcanic vents. 
"These processes may have contributed somewhat to the 
hardening of the Brazilian reefs, but they do not setmi compe- 
tent to account for them altogether. These theories are 
especially incapable of accounting for the lithification of 
beaches behind older reefs." 
'"The distribution of the consolidated beaches of northeast 
Brazil leads to the inference that the consolidation is directly 
related to the densitv of the sea water." 
