186 BULLETIN : MUSEUM OF COMPARATIV^E ZOOLOGY. 



beaches of all tropical seas solidified by lime deposits. It is unnecessary 

 to say that such is not the case. So far as mere temperature goes, the 

 surface waters along the northeast coast of Brazil are probably neither 

 warmer nor colder than those along the shores in many other places 

 within the tropics. And yet the northeast coast of Brazil is almost the 

 only one along which the beaches have been extensively solidified. 



In view of the exceptional character and extent of the stone reefs of 

 Brazil, it must be admitted that the theorj" of the deposition in them of 

 lime carbonate, due solely to the increase of the temperature of the water, 

 is not satisfactory. 



III. Lime carbonate from the land. — Waters flowing from a land sur- 

 face of limestone would necessarily be charged with lime. If such 

 streams entered the sea without other dilution, there would be a ten- 

 dency for them to deposit their lime contents immediately upon entering 

 the sea. This precipitation is due to the saturated condition of the two 

 waters. The Rhone, emptying its strong lime waters into the Mediter- 

 ranean Sea, deposits lime with its silts, and the beaches about its mouth 

 are in many places consolidated. Lyell remarks, in speaking of this mat- 

 ter : " If the number of mineral springs charged with carbonate of lime 

 which fall into the Rhone and its feeders in different parts of France be 

 considered, we shall feel no surprise at the lapidification of the newly 

 deposited sediment in this delta." ^ 



The rocks of western Palestine and of southern Asia Minor are made 

 up almost entirely of limestone, so that the streams flowing from that 

 land surface enter the already dense waters of the Mediterranean Sea 

 heavily charged with lime, and the precipitation of that lime on the 

 shores has made the reefs and consolidated beaches described by Beau- 

 fort,2 Botta,8 Lartet," and Hull.^ 



Inasmuch as the stone reefs of the Levant seem to be about the only 

 extensive ones in" the world compai-able with those of northeast Brazil, it 

 seems best to give here some account of them and of the conditions un- 

 der which they appear to have been formed, in the hope of getting light 

 upon the Brazilian stone reefs. 



1 Charles Lyell, Principles of geology, ed. 11, I., p. 426. New York, 1889. 



2 F. Beaufort. Karamania, p. 10, 13. 174, 178, 207, 211, 212, 253, 289. On lime 

 in the streams, p. 130, 135-136, 141, 191, ed. 2. London, 1818. 



3 Observations sur le Liban, etc. Mem. Soc. Geol., France, ed. 1, p. 135-160. 

 * L. Lartet. Exploration geologique de la Mer Morte. Paris, 1877. 



5 E. Hull. The survey of Western Palestine. Physical geology and geography. 

 London, 1886. 



