CORALS AND CORAL ARCHITECTURE. 



269 



continue indefinitely around the margins. Thus, in many places, the 

 tops of adjacent trunks have joined together, forming a coral floor 

 resting upon arches and pillars built without axe or sound of hammer. 

 In some parts of the reef-region, such united coral-heads cover large 

 areas. A magnificent scene would be presented should the waters re- 

 cede and leave bare these arches and columns. The ruins which " sen- 

 tinel the desert " would not rival them in grandeur. To thread their 

 avenues and sounding aisles would be the labor of a lifetime. 



The illustration, Fig. 12, after a sketch by Prof. C. F. Hartt, 

 in his " Geology of Brazil," is of an area of the sea off that coast, 

 abounding in coral-heads similar to those described. " The corals," 

 says Prof. Hartt, " grow in the open sea, and often rise 40 or 50 

 feet, and form what the natives call cJiapeiroes (signifying ' big hats ') # 



Fig. 12. 



Coral-headi oil the Brazilian Coast. 



They are abundant on one part of the coast over an area of 40 square 

 miles. A vessel running on the top of one of these chapeiroes w r ould 

 remain perched like a weathercock on the top of a tower, to the great 

 amazement of the captain who finds deep water all around." Inside 

 the outer or barrier reef the water is smooth as in an inland bay. If 

 free from sediment, and not freshened by discharge from rivers, it is 

 the paradise of the smaller corals. The beautiful fungia lie with innu- 

 merable shells upon the bottom. The feathery and fan corals grow in 

 clusters, and, amid their delicate plumes, fishes, which rival them in 

 gayety, glide through the transparent water. 



It is a peculiarity of coral-reefs that the outer side is usually nearly 

 perpendicular, w T hile the inner side is a gentle declivity. The cause 

 of this may be better understood if we follow the development of 

 the reef from its beginning. Upon a shore of sand or rock, and 

 at a depth of less than 120 feet, the reef-builders attach themselves 



