92 CORAL FORMATIONS. 
proportion, from four analyses, is 10,000 to 371.* Schweitzer obtained 
the following result for water taken from the British Channel.t+ 
Water - - - - - - 964-74 grains. 
Chlorid of sodium —- - - - - 27065 cs 
Chlorid of potassium - - - - - OT ccs 
Chlorid of magnesium - - - : S:6ue se 
Bromid of magnesium - - - - 003 « 
Sulphate of magnesia - - - : “ 2°29 « 
Sulphate of lime - - - = eee 1 
Carbonate of lime - - - - - 0:03 « 
4000-00 
Recently, Mr. G. Wilson has detected fluorine in sea-water, show- 
ing that all the ingredients of coral are actually contained in the 
waters of the ocean.t 
It has been common to attribute the origin of the lime of corals to 
the existence of carbonated springs in the vicinity of coral islands. But 
it is an objection to such an hypothesis, that in the first place the facts 
do not require it; and in the second, there is no foundation for it. 
The islands have been supposed to rest on volcanic summits, thus 
making one hypothesis the basis of another. Carbonic acid springs 
are by no means a universal attendant on volcanic action. ‘The 
Pacific affords no one fact in support of such an opinion. There are 
none on Hawaii, where are the most active fires in Polynesia; and 
the many explorations of the Society and Navigator Islands have 
brought none to light. Some of the largest reefs of the Pacific, those 
of New Holland and New Caledonia, occur where there is no evidence 
of former volcanic action. § 
The currents of the Pacific are constantly bearing new supplies of 
water over the growing coral beds, and the whole ocean is thus 
engaged in contributing to their nutriment. Fish, molluscs, and 
zoophytes are thus provided with earthy ingredients for their calca- 
reous secretions, if their food fails of giving the necessary amount; 
* On Comparative Analytical Researches on Sea Water, by Prof. Forchhammer,— 
Rep. Brit. Assoc. for 1846, p. 90. 
+ Lond, and Ed. Phil. Mag. for July, 1839, xv. 51; Amer. Jour. Sci., xxxviii. 12. 
t Trans. Roy. Soc. of Edinburgh, xvi. 145, 1846; Amer. Jour. Sci. 2d ser. ii. 114, 1846. 
§ See also Darwin, op. cit. p. 60. 
