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ALGAL STALACTITES IN BERMUDA 



By John W. Harshberger 



The hills of Bermuda are formed of a friable limestone, which 

 represents particles of calcareous sand, which in the early geologic 

 history of this group of islands was drifted by the wind into 

 elevated dunes and afterwards by water action was compacted 

 into a harder, or a softer, lime rock. This native rock is sawed 

 out of the hillsides and is used in the construction of house, 

 walls (large, thick blocks), or house roofs (large, thin slabs). 

 When exposed to the air, this soft quarried rock hardens into a 

 form of limestone, much like concrete in appearance. As in all 

 limestone formations of any considerable thickness, caverns and 

 underground tunnels are worn into the softer strata by the action 

 of rain, and underground water. Several caverns of this char- 

 acter are visited by tourists in Bermuda and some of them have 

 pools of salt-water replenished by underground supplies from the 

 ocean. There are limestone sinks, which represent caves, the 

 roofs of which have fallen in. A number of these sinks are dry, 

 others are filled with water. One of the most frequently visited 

 ■of these depressions, filled with saltwater, which comes under- 

 ground from the ocean, is Devil's Hole in which are kept a 

 number of the characteristic fishes of the Bermuda archipelago, 

 such as, the grouper, the angel-fish, the red-snapper and others 

 equally celebrated. The walls of the Devil's Hole are rather 

 steep, and in places overhanging, so that the fresh water from the 

 rocks above drips into the pool beneath. Here were found 

 stalactites from an inch to two inches in length and coated with a 

 covering of blue-green algae. 



Several of these stalactites were broken off from the overhanging 



wall in Devil's Hole, June, 1905, and kept dry for subsequent 



study, but the material was overlooked until the present summer 



(1914), when a study was made of it. Small pieces of stalactite 



were crushed in water and examined under the microscope. The 



blue-green algae, which alone were present, were identified with 



Josephine Tilden's* first volume of Minnesota Algae. The algae 



* Tilden, Josephine. Minnesota Algae. Volume I. The Myxophyceae of 

 North America and Adjacent Regions, including Central America, Greenland, 

 Bermuda, the West Indies and Hawaii. Bot. Ser. VIII, 1910. 



