104 RATE OF GROWTH. Ch. IV. 



in certain large areas where subsidence has probably 

 been long in progress, the growth of the corals has 

 been sufficient to keep the reefs up to the surface ; and 

 this is a much more important standard of comparison 

 than any cycle of years. 



It may, however, be inferred from the following 

 facts, that the rate under favourable circumstances 

 would be far from slow. Dr. Allan of Forres has given, 

 in his MS. Thesis deposited in the library of the 

 Edinburgh University, the following account of some 

 experiments, which he tried during his travels in 

 the years 1830 to 1832 on the East Coast of 

 Madagascar. ' To ascertain the rise and progress 

 of the coral family, and fix the number of species 

 met with at Foul Point (lat. 17° 40'), twenty spe- 

 cies of coral were taken off the reef and planted 

 apart on a sand-bank three feet deep at low water. 

 Each portion weighed ten pounds, and was kept in 

 its place by stakes. Similar quantities were placed 

 in a clump and secured as the rest. This was done in 

 December 1830. In July following, each detached 

 mass was nearly level with the sea at low-water, quite 

 immovable, and several feet long, stretching, like the 

 parent reef, in the line of the coast-current from north 

 to south. The masses accumulated in a clump were 

 found equally increased, but some of the species in 

 such unequal ratios as to be growing over each other.' * 

 The loss of Dr. Allan's magnificent collection by 



1 I owe the above extract to the kindness of Dr. Malcolmson. 



