244 REACTION OF THE INTERIOR OF THE EARTH 



Kosima ( 34 ), described by Horner and Tilesius, at the en- 

 trance of the Tsugar Straits, do not rise 1000 feet above 

 the waters, while others, as the Peak of Teneriffe ( 341 ), 

 are 12,000 feet above the sea have been actually 

 upheaved by the volcanic forces from a sea-bottom often 

 above 21,000 feet, and sometimes even nearly 46,000 

 feet deep. It is also important to remark, in order 

 to avoid erroneous inferences from the subjoined nu- 

 merical relations, that if between volcanoes of the 1st 

 and the 4th class, i.e. between volcanoes of 1000 and of 

 18,000 French feet (1066 and 19,184 English feet), the 

 differences appear very considerable, yet the propor- 

 tion between these numbers becomes greatly altered 

 if (in conformity with Mitscherlich's experiments on 

 the fusion-temperature of granite, and according to the 

 not altogether probable hypothesis that the heat in- 

 creases uniformly in arithmetical progression with in- 

 creasing depth) we assume the upper limit of the 

 molten interior of the earth to be about 121,500 feet 

 below the present level of the sea. The differences of 

 height between known volcanoes are, we may well be- 

 lieve, not considerable enough to authorise us to expect 

 that the height of the highest should present any 

 materially increased obstacle to the effects of the tension 

 of elastic vapours (powerfully increased when pent up 

 by the stoppage of volcanic fissures) in forcing lava and 

 other dense substances up to the crater. 



