178 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



Carbon dioxide of submarine volcanic origin. — The carbon dioxide 

 ordinarily found in tlie sea is not free but combined in carbonates and 

 bicarbonates. 



In the case of carbon dioxide of volcanic origin discharged in the sea, 

 it might remain chemically dissolved in the water, (CH2O + CO2) = 

 (H2 CO3), but as soon as it came in contact with calcium or magnesium, 

 the carbon dioxide would dissolve the lime carbonate, -whether in the 

 calcareous shells of living niollusks, corals, and crustaceans, or in the 

 broken fragments of dead ones on or near the shores, A bicarbonate 

 would be formed and held in solution until precipitated out or other- 

 wise removed as a carbonate. 



It is but natural that one should object at the outset to a theory that 

 seems to be so far-fetched — to a source so out of the ordinary course of 

 events as does the one here suggested. But the source is really not so 

 extraordinary as it at first appears. 



The most valuable observations upon the gases emitted by volcanic 

 eruptions with which I am acquainted is that of Fouque upon " Santorin 

 et ses eruptions," published at Paris in 1879. In his study of that 

 interesting locality M. Fouque found that — 



a. The carbonic acid discharges became more and more marked after 

 the seasons of greatest volcanic activity. 



b. That the compositions and temperatures of gases were but little 

 affected by passing through waters (p. 229). 



c. That variation of the gases is the same for subaqueous as for 

 subaerial volcanoes (p. viii). 



The pouring out of volcanic eruptions beneath the ocean is not an 

 uncommon occurrence. Indeed, Sir Archibald Geikie lately remarked 

 that " With regard to the supposed impossibility of lavas having flowed 

 under the sea, he could only observe that no facts in the geological 

 history of Britain were more abundantly proved than that from the 

 earliest Palaeozoic periods the vast majority of the volcanic eruptions in 

 our region have been submai'ine." ^ . . . Sometimes the products of these 

 eruptions rise above the water's sui-face, forming islands, as in the cases 

 of Graham's Island in the Mediterranean Sea,'^ islands off the west coast 

 of Iceland, and Bogoslof off the island of Unalaska. 



The island of Bogoslof, as it is now called, was first described by 

 Langsdorflf. He says that in 1795 the people of Unalaska observed the 



1 Quar. Journ. Geol. Soc, May, 1898, LIV., p. 233. 



2 II. J. Jolinston-Lavis. For bibliography of this island, see The south Italian 

 volcanoes, p. 105-107. Naples, 1891. 



