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accepts it. We may therefore imagine that this point of the controversy is 
still open. In regard to Professor Dana’s objection that Mr. Darwin has not 
laid sufficient weight on temperature in the distribution of coral, it seems to 
us that he not only has done so, but that he has gone into many other 
questions on this point. Still we cannot say that he has completely made 
out the reason why it is that coral reefs abound in certain localities, and 
are as completely absent from other places which have conditions exactly 
identical. Indeed, it appears to us that the question is still one of those 
many problems which are at the present moment utterly insoluble. 
Another point of difference between the two authors is as to the effect of 
volcanoes upon coral reefs. Mr. Dana considers that these eruptive 
mountains have an impeding influence on coral growth, and so un- 
doubtedly they have when excited. But Mr. Darwin’s question as to how 
the volcano can influence a large district clearly shows that the objection 
has no real value. The other question which Mr. Dana raised was, we may 
mention, fairly met by Mr. Darwin, when treating of the entire subject, in 
that spirit of thorough fair play which we have so frequently admired when 
studying his different books. There are many other points in connection 
with this subject which we should wish to touch on, but inexorable space 
prohibits. However, there are one or two we must refer to, and these are 
the rate at which coral grows, and the depths at which it can and 
can not live. The first question is one which is frequently answered, but in 
no instance is it more fully replied to than in the quotation from Dr. 
Allan’s MS. thesis : — “ 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 species 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 follow- 
ing each detached mass was nearly level with the sea at low water, quite 
immovable, and several feet long, stretching like the parent reef, on the 
line of the coast current from north to south.” This shows clearly enough 
the tremendous rate of growth which corals have. And although, from the 
loss by shipwreck of Dr. Allan’s splendid collection, the exact species has 
not been determined, yet it was thought by him to have been a Madrepore 
which grew at the most rapid rate. 
The other point in which we must quote from our author is as to the depth 
at which corals will maintain themselves. It seems that they u wholly dis- 
appeared at a greater depth than 20 fathoms on the slope round Keeling 
Atholl, off the reefs in the Pacific (according to Dana), on the leeward side 
of the Mauritius, and at rather less depth both within and without tbe 
atolls of the Maldiva and Chagos Archipelagoes ; and when we know that 
the reefs round these islands do not differ from other coral formations in 
their form and structure, we may, I think, conclude that in ordinary cases 
reef-building polypifers do not flourish at greater depths than between 20 
or 30 fathoms, and rarely at above 15 fathoms.” From this it seems clear 
enough, but there are many other facts that point to the same conclusion. 
We hope we have said and abstracted enough of this clever book to induce 
the reader to take it up himself. If so, we have done sufficient. Still, if it 
