244 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1926 
abstract carbonate of lime from the sea water and so deposit it that 
it reproduces their own radiated structure. All the structural works 
of man fade into nothingness when compared with the results of the 
life activities of the minute foraminifera and the coral polyp. Hoy- 
born calculates that the limestones and dolomites contain twenty-five 
thousand times the amount of carbon dioxide now present in the air. 
And chalk is still forming over 50,000,000 miles of ocean bottom. 
In its metamorphosed form of marble, limestone exhibits the widest 
possible range of texture, color, and degree of purity. In it the 
greatest sculptors have found a medium for their best expression, 
and of it were built the exquisite lacelike fabric of the Taj Mahal 
and the structures which were the glory of Greece and Rome. The 
pearl, which in all ages has been associated with beauty and with 
riches, is in reality no more than a brilliant sarcophagus of carbonate 
of lime formed around an intruding parasite by the pearl oyster. 
There are, nevertheless, as Browning says: 
“Two points in the adventure of the diver— 
One, when a beggar he prepares to plunge; 
One, when a prince he rises with his pearl.” 
Like all carbonates, the pearl dissolves in weak acids with evolu- 
tion of carbon dioxide. When, therefore, Cleopatra dissolved the 
pearl in vinegar she prepared the most expensive carbonated drink 
that history records. 
CLIMATIC INFLUENCE OF CARBON DIOXIDE 
Despite the minute proportion of carbon dioxide in the atmosphere 
its climatic influence is of extraordinary importance. The blanket 
which keeps the earth warm is composed wholly of carbon dioxide 
and water vapor, which absorb the heat that would otherwise be 
radiated from the earth. According to Arrhenius the removal of 
all carbon dioxide from the atmosphere would cause the tempera- 
ture of the earth’s surface to drop 37° F. The quantity of water 
vapor would, therefore, so diminish as to cause an almost equal 
drop, and the whole earth would be bound in Arctic ice. Thus an 
increased and uncompensated fixation of carbon dioxide by the 
rocks would bring on a new glacial period, whereas a slight aug- 
mentation of its proportion in the atmosphere would restore the 
tropical climate and the exuberant vegetation of the Carboniferous 
Age. Fortunately, there is now maintained a delicate balance in 
the carbon cycle in nature. The ocean is estimated to contain forty 
times as much carbon dioxide as the atmosphere, and, as equilibrium 
is disturbed by the fixation of carbon dioxide by the rocks and plants, 
a compensating portion of the ocean reserve passes into the air. 
