,907.] AND MOUNTAIN FORMATION. 391 



sea pass unnoticed. It is not remarkable, therefore, that we find so 

 few volcanoes in this region, and the absence of known volcanoes 

 in no way contradicts the theory. Volcanoes usually break out after 

 mountain ridges are folded sharply upward; this stage may come 

 later in the South Atlantic, where the sea is neither very deep nor 

 the gradient very steep near the shores. Consequently in such a 

 region we should not expect at present many volcanoes or great 

 visible earthquake effects. 



2. Some geologists have believed also that the steam escaping 

 from, volcanoes coxites from the central magma of the globe. But 

 if this were true, as we have pointed out in the paper on the " Tem- 

 perature of the Earth" (p. 288), the volcanic outbreaks ought to 

 occur in the interior of the continents as well as near the oceans. 

 For the vapor ascending from the central magma of the globe could 

 not always be deflected around the immense extent of the continents, 

 and appear only at their edges, and in the depths of the sea. The 

 geographical distribution of volcanoes therefore effectively contra- 

 dicts any such hypothesis. 



§ 15. The Criticism based on the Supposed Coincidence of Great 

 Earthquakes idth the Sudden Shifting of the Earth's Axis in its 

 Revolution about the Mean Axis of Figure. — A reviewer of the 

 paper on the '' Cause of Earthquakes," in Nature, August i, 1907, 

 after admitting the adequacy of the cause assigned to explain most 

 phenomena finally adds : 



"But his (See's) explanation fails to account for the remarkable connec- 

 tion between the irregular shifting of the earth's axis and the occurrence of 

 the greatest earthquakes. That these irregular movements of the axis are 

 greatest when large earthquakes are most frequent is a certain, but as yet 

 unexplained, fact; it seems to necessitate displacement of matter in the earth 

 on a far larger scale than is indicated by the differential measurements which 

 alone are open to us. Professor See's explanation, though it provides for 

 lateral and vertical displacement of matter, necessitates the elevations and 

 depressions being so closely contiguous as practically to neutralize each 

 other's effects, and, therefore, fails as an explanation of the ultimate cause 

 of earthquakes, while it in no way affects the current acceptance of fracture 

 as their immediate cause." 



This criticism is not well founded, and after what has been said 

 above and in the two preceding papers, probably does not require 



