RATE OF GROWTH OF' CORALS. 127 



breaking three inches of coral crust I found the collar bone 

 of a man, a brass regulating screw belonging to a quadrant, 

 and some large lead bullets. * * * The magazine must 

 be under the branch-coral, which has been sixty-four years 

 growing. * * * 



Here we have a height of sixteen feet in a Madrepora 

 attained in sixty-four years, or at the rate of three inches a 

 year. Madrepores evidently grow with much greater rapidity 

 than the massive corals. 



Observations on the rate of growth of different species 

 might easily be made by those residing in coral seas, either in 

 the manner adopted by Mr. Allan (placing the specimens on 

 a platform which could be raised for examination from time 

 to time — say every five years), or by placing marks upon par- 

 ticular species where they are immovably fixed to the bottom. 

 By inserting slender glass pins a certain distance from the sum- 

 mit of a Madrepore, its growth might be accurately measured 

 from month to month. Two such pins in the surface of an 

 Astrcea, would in the same manner, by the enlarging distance 

 between, show the rate of increase in the circumference of 

 the hemisphere ; or if four were placed so as to enclose an 

 area, and the number of polyps counted, the numerical in- 

 crease of polyps resulting from budding, might be ascer- 

 tained. If specimens are selected, as done by Mr. Allan, it is 

 important that they should be placed where other corals are 

 growing in luxuriance, so as to be sure that there are no dele- 

 terious influences to retard growth. It is to be hoped that 

 some of the foreign residents at the Sandwich, Society, Samo- 

 an or Feejee Islands will take this subject in hand. There are 

 also many parts of the West Indies where these investiga-' 

 tions might be conveniently made. 



