336 SECONDARY FORMATIONS. [Ch. XXIII. 



submarine eruptions ; but at some points,, as in the Hebrides, 

 it seems that the same ocean was the theatre of volcanic action. 

 We have mentioned in the first volume *, that as the ancient 

 eruptions occurred in succession, sufficient time usually inter- 

 vening between them to allow of the accumulation of many 

 subaqueous strata, so also should we infer that subterranean 

 movements, which are another portion of the volcanic pheno- 

 mena, occurred separately and in succession. 



* Chap. v. p. 88 ; and Second Edition, p. 100. 



