THEORY OF THE EARTH. 447 



period of repose in the earth, in which animals were 

 multiplying, and is therefore a great deposit; as it may 

 he a group by containing interposed shales and sand- 

 stones; these marking the joint degradation of the 

 land : while an excess of non-calcareous strata needs 

 not give rise to a separate one. Secondly, that another 

 group can he formed of a continuous mass of alterna- 

 ting shales and sandstones ; animals having disappeared, 

 or become rare: while here also, a few calcareous beds, 

 especially in the upper portions, need not impede such a 

 separation. Yet should the limits be undefined in 

 practice, thus leading to differences of opinion, we must 

 console ourselves by recollecting that we cannot do more 

 than Nature has done. And if Geologists will now show 

 that they have distinguished the upper strata in this 

 manner, we shall begin to understand each other; or 

 rather, if they will hereafter do what they have not yet 

 done, and farther, trace the geographical limits of these 

 groups, principal or subsidiary, in the world, or even 

 in Europe, we shall then discover how far remote strata 

 and sets of strata correspond, and know, at least, some- 

 ' what more of the agreement of ;c Germany" and " Eng- 

 land" than from a comparison of their respective cockles. 

 But I shall not end these remarks without adding, that 

 if the circumstances which I have pointed out as to 

 the conditions of the earth following the coal should 

 be established, the classification formerly given will re- 

 quire essential alterations. 



The last subsidiary branch of the Theory of the 

 Earth, as far as anterior to its present condition, in- 

 cludes the partial deposits, so much confounded under 

 the vague term "tertiary." I was unwilling to pro- 

 pose the entire disentanglement of this subject for- 

 merly : I must here endeavour to do what a general 

 Theory demands. That some deposits more properly 

 belonging to the alluvia, should coincide or be con- 



