xxxiv Appendix. 
Such is an outline of what I propose to call the Herschel-Babbage theory, 
after the two distinguished philosophers who originated it ; it has the advan- 
- tage over all other theories of the same nature of being capable of being proved 
or disproved by observations in the field. When firmly established, as I 
believe it will be, it will throw a new light on geology, for it gives significance 
to the thickness and composition of every rock, and to its geographical position ; 
it gives significance to every bend and fold in the strata, to every fault and 
volcanic dyke ; and it will also be found to furnish us with a key that will 
decypher many of the hitherto obscure passages in geological history. 
