8 MR GOODCHILD ON 
later into the sulphate. It will presently be shown that 
these facts are of considerable importance in relation to 
coral reefs. More than one-third of the ocean floor receives 
little or no carbonate of lime in the solid form on account 
of this solvent action of sea-water at great depths. 
Notwithstanding the apparently-large amount of car- 
bonate of lime present in the surface-waters of the ocean, 
the rate of deposition, even under the most favourable 
circumstances, would appear, from certain facts lately made 
known, to be extremely slow. Professor Martin Duncan, in 
his Presidential Address to the Geological Society of London 
(vol. xxxili. p. 74), says :—‘ I have satistied myself from late 
researches that the rate of deposition is extremely slow. 
Thus, an electric cable was laid down in the Globigerina 
Ooze region, and, five years after, a considerable coral growth 
had taken place on it. Some of the living calices were 
close above the cable, and therefore the deposit had been 
infinitesimal in that time.” Mr Mellard Reade estimates 
the rate of growth of this chalky mud at less than one foot 
in 20,000 years. My own independent estimate, based upon 
other data, makes the rate to be one foot in 41,985 years— 
say one foot in 40,000 years, to put the statement into 
round numbers. To this it may be added that certain facts 
connected with the Chalk seem to lend support to the view 
that the rate of deposition of this chalky mud must have 
been very slow. 
Reference to this has been given at some length, because 
the view of the origin of coral reefs advocated by Sir John 
Murray (which I may as well state here that I accept as, 
on the whole, the best that has been put forward) involves a 
reference to the rate of growth of these submarine deposits 
of carbonate of lime. 
It may conduce to a clearer understanding of the subject 
if the successive stages in the formation of calcareous de- 
posits on the sea bottom are summarised here. These stages 
are as follows :— 
(1) The uprise of eruptive masses from the interior of the 
earth, and their subsequent exposure to atmospheric agencies. 
(2) Liberation of bicarbonate of lime through the solvent 
