RATH OF GROWTH OF CORALS. L237 
breaking three inches of coral crust I found the collar bone 
of a man, a brass regulating screw belonging to a quadrant, 
sian eee fale 
and some large lead bullets. The magazine must 
be under the branch-coral, which has been sixty-four years 
meawing, ~ ~ * 
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. Observations of Prof. Joseph Le Conte on Madre- 
pora growths at the Tortugas in 1851 (American Journal 
of Science, 1875) lead to a rate of 3} inches a year. 
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 
Astra, 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 arc 
also many parts of the West Indies where these investiga- 
tions might be conveniently made. 
