28 
GEOLOGY: A. G. MAYER 
SUB-MARINE SOLUTION OF LIMESTONE IN RELATION TO 
THE MURRAY-AGASSIZ THEORY OF 
CORAL ATOLLS 
By Alfred Goldsborough Mayer 
DEPARTMENT OF MARINE BIOLOGY, CARNEGIE INSTITUTION OF WASHINGTON 
Received by the Academy, December 9, 1915 
In 1880 Murray^ advanced the idea that the solvent action of sea- 
water for limestone was a primary factor in the deepening and widen- 
ing of the lagoons of coral atolls. This idea was afterwards adopted by 
Alexander Agassiz^ who became its most active advocate. In 1914 Dole* 
made a chemical study of the water of the lagoon of the atoll of Tortugas, 
Florida, and decided that it contained no free carbon dioxide, and 
Tashiro^ pursuing a different method decided that if free carbon dioxide 
be present in Tortugas sea-water its amount must be slight. In view 
of these facts Vaughan^ stated that lagoons of atolls could not have 
been dissolved out by sea-water as such, but he gave no quantitative 
data to support this view. The validity of the Murray-Agassiz theory 
depends upon the rate of the solution of limestone in atoll lagoons. 
Elschner^ states that the solubility of calcium carbonate in sea-water is 
extraordinarily low but he also gives no quantitative data. I have 
made an attempt to determine the rate of solution of calcium carbonate 
in Tortugas sea-water. Carefully weighed pieces of the shell of the 
mollusc Cassis having a specific gravity of 2.88 and areas ranging from 
57.6 to 85 sq. cm. were treated as follows: 
Shell No. 1 was placed for 367 days in a sealed, steriHzed, glass carboy 
containing 45 liters of doubly filtered sea-water, which after being 
filtered was heated within the carboy to 72.5°C. for two hours. At the 
end of the year this sea-water still retained 71% of its alkalinity to 
phenolphthalein test. No bacteria or other visible growths developed 
within this carboy and the shell remained clean and without slime upon 
its surface. This shell weighed 13.285 grams in July, 1914 and at the 
end of the year it had lost 0.014 gram. Thus it would have taken 948 
years to dissolve the shell, and a thickness of 0.00067 mm. was removed 
from its surface by one year's immersion. 
Shell No. 2 was placed in another similar carboy, but the sea- water 
was neither filtered nor sterilized, and it developed bacteria, protozoa 
and algae, and at the end of the year it was acid; its free acidity over and 
above neutrality by phenolphthalein test being equivalent to 3^ H2SO4. 
The shell originally weighed 15.532 grams and it lost 0.173 gram after 
360 days. Hence it would have taken 90 years to dissolve the shell, 
and a superficial thickness of 0.007 mm. was removed in one year. 
