76 REPORT — 1876. 



tion. He has admitted " Gaps" — breaks, that is to say, for which he finds no equi- 

 valents in the British series — the strata that should occupy these gaps having been 

 either removed by denudation or never deposited, the British area being at these 

 times above water. The concession is fatal to the scheme. But the very use of 

 the word gap recalls the phrases " complete " and " incomplete," and their nearest of 

 kin, " base of a formation." Prof Ramsay used the word '"'break" to mark his 

 unconformities ; but no term has been proposed for " the base of a formation." The 

 term was in constant use when such base was always claimed to be a conglo- 

 merate. That notion is now exploded ; but no distinction is drawn between the 

 lowest bed of a group of conformable strata, and the bed or beds which repose 

 unconformably on those below them. Thus the London Basin has the Thanet beds, 

 the Reading beds, and the London Clay successively resting on the Chalk ; and each 

 of these is the base for its proper locality, unless it be asserted that in this and 

 similar cases the lowest beds once covered a wider area and were then removed. 

 But a more important case is presented by the great calcareous accumulations of 

 the Carboniferous and Chalk series. The Lower Greensand is to the latter series in 

 England what the lowest stratum of the chalk would be if we could get at it. The 

 C'arboniferous Limestone rests directly on the Red Sandstone iu Central England ; 

 further north it rests on the Calciferons Sandstones. Thus the base of the forma- 

 tion varies according to locality, or rather according to the circumstances of depo- 

 sition; and we need a term which would indicate a difference between the conform- 

 able and unconformable succession. JNIr. Judd has lamented the equivocal use, by 

 English writers, of the term formation, which etyniologically is as well applied to the 

 Chalk without flints as to the whole Cretaceous series. Pie advocates " system " as 

 applicable to the larger groups — the Cretaceous system fn* example. But it seems 

 as if the time were come for still further restrictions of either or both terms. 



The analogy of the geological record to an incomplete volume is, like most 

 analogies, at once imperfect and misleading. Rather might the record be compared 

 to the fragments of two volumes which have come to be bound together, so that it 

 is not possible to recognize the sequence. Or perhaps it might be better compared 

 to a universal history in which, by omission of dates, the chronology is thoroughly 

 obscured, and the necessary treatment of each nation by itself conceals the con- 

 temporaneity of events. V\^e have the aquatic record and the terrestrial record : and 

 these two are going on simultaneously. It is as yet, and probably always will be 

 injpossible to recognize the marine deposits which correspond to the terrestrial 

 remains, save perhaps in the most recent geological times. We now know that 

 the life of the Cretaceous seas is not wholly extinct in the existing Atlantic Ocean, 

 but exists there to an extent which would entitle the deposits of that area to rauk 

 by the statistical method as intermediate between the Cretaceous and the Tertiary. 

 It is obviously impossible to include under one term deposits which are associated 

 with geographical changes so important as those commonly accepted as having 

 prevailed during the Tertiary epoch. The iNIesozoic forms pass gradually into the 

 Tertiary; how gradually we cannot say, since the deep-sea equivalents of the 

 European Tertiaries are not certainly known to us. But as a jiortiou survives to 

 the present day, and as, presumably, the extinction was not rapid (for it is only iu 

 the case of land-animals that sudden disappearances are as yet probable), it is obvious 

 that the successor, the heir, of the Chalk was not the Eocene, nor necessarily the 

 Miocene known to us, but probably deposits still buried under the Atlantic. 



]\Iy object is to show that even the limitation of time which Prof Tait pre- 

 scribes for us may not after all be too narrow for the processes which have resulted 

 in our known stratigraphy. Mr. Darwin speaks of the geologic record being the 

 imperfect record of the last series of changes, the indefinite extension of time anterior 

 to the earliest fossiliferous rocks being necessary for the full evolution of organic 

 forms. But is there any ground for the assumption ? True that the Laureiitians 

 contain fragments of antecedent rock; but were these fossiliferous ? Are they the 

 remains of land surfeces on which living beings flourished ? or are they only the 

 debris of the first consolidated portion of the Earth's crust, on which if organisms 

 existed they may have been the most primitive of our organic series ? Mr. 

 Jukes refers to the possibility of sucli earlier strata having existed ; but he wrote 

 ■when geologists were dominated by the belief iu the indefiniteness of geological 



