198 Proceedings of the Royal Physical Society. 



deposition." We may, and must as far as we can, establish 

 a similarity of order — homotaxis, as it has been termed — 

 between the strata of different regions, but similarity of 

 order is not to be confounded with synchrony of deposit ; 

 and we must, therefore, if we would place the solutions of 

 our science on a philosophical basis, abandon, as all sound 

 geologists are rapidly abandoning, the idea that specific 

 identity of fossil forms is proof of stratigraphical contempo- 

 raneity. 



Quaternary accumulations. — Another point materially 

 affecting the present position of our science, and one of 

 the last to which our time will permit me to refer, is the 

 very unsatisfactory arrangement of the. post-tertiary, qua- 

 ternary, or superficial accumulations. It is true we may 

 generally classify them according to the agents by which 

 they have been formed, or, in other words, according to their 

 composition and the causes by which they have been pro- 

 duced. In this way we have fluviatile, lacustrine, marine, 

 chemical, organic, and igneous accumulations, but this con- 

 veys no idea of succession or history in time. What our 

 science requires is, that we endeavour to arrange them in 

 chronological order, as we have done with the earlier sys- 

 tems. The arrangement proposed by the late Dr Fleming 

 into taragmite, akumite, and phanerite is so purely hypo- 

 thetical, and so obviously at variance with observed facts, 

 that it has not been, and cannot indeed be accepted. The 

 broader arrangement into pre-human and human periods 

 is obviously too general to be of much advantage to working 

 geologists, at the same time that it can give us no clue to 

 determine when the pre-human ends and the human begins. 

 Again, such terms as the <l Leda clay" of the St Lawrence 

 and the " Saxicava sand" of Montreal, though good and dis- 

 tinctive enough for local purposes, are inappropriate for 

 other regions ; and others, as " Pampean formation," " Erie 

 clay," and the like, merely announce a geographical fact, 

 without conveying any idea either of fossil remains or chro- 

 nological sequence. Had the post-tertiaries, like most of 

 the tertiaries, been strictly sedimentary, some percentage 

 system of fossil forms like that by which Sir Charles Lyell 



