On the Domite Mountains of Central France. 149 



but to calculate the height at which such a cone would have to 

 give way would involve more mathematics than I am master of, 

 and it has no immediate bearing on my subject.) If we suppose 

 this same cone to have been filled with the lighter lava, or 

 Domite, the pressure of a column of this lava of the same height 

 would only have been some sixty-six atmospheres, or 1,000 lbs. on 

 the inch square, against 1,200 ; or in other words, it would have 

 taken a column of the Domite lava 960 feet in height to produce 

 a pressure equal to a column of the Basaltic lava 800 feet high. 



So that as a matter of fact this Domite lava, supposing it to 

 have been discharged from a crater of a conical form, as from 

 all analogy we have strong reasons for thinking it must have 

 been, could have acted in no other way than that which I have 

 endeavoured to describe, and would thus have produced bowl- 

 shaped masses of the appearance presented in Auvergne. 



SciEN. Pboc. , E.D S. Vol. hi., Pt. in. 



