— M 
BRANNER: THE STONE REEFS OF BRAZIL. 191 
The accompanying map taken from the chart of the “Challenger” Re- 
ports, Physics and Chemistry, Vol. I., shows the areas of densest sea- 
waters over the globe. The variation in density must be due to the 
different rates of evaporation. The almost closed basins of the Medi- 
terranean and Red Seas are in warm, arid, or partially arid regions, where 
evaporation goes on very rapidly. Some of the streams entering these 
ERST f ПА Р 
INDEX. 
Ши | | sore 10280 
ПШ between 1.0275 and 10280 |! 
в 10870 , 10875 
» 10265 о 10270 
10260 „ 10265 
m 10258 , 1.0260 
n 10250 , 1:0245 
10240 
below 
ШШ 
Fie. 95. Surface densities of sea waters (“Challenger ”). 
basins are heavily charged with lime, so much so that fresh-water tufa 
deposits are forming at many places on a large scale. On entering the 
sea the dense salt waters tend to hasten the deposition of the lime, and 
this takes place most readily upon the beaches where evaporation is 
most rapid. 
The area of high sea-water density on the northeast coast of Brazil is 
probably to be attributed to rapid evaporation on the surface of the 
