81 
others allow of the occasional occurrence of violent perturbations, 
affecting the condition of sea and land, and originating in 
unknown and unobservable causes. According as the one or 
the other of these views is taken, the chronology of geology 
will be widely different. The system of Lyell demands, in fact, 
the concession of ages of inconceivable duration to account for 
the changes in the earth and its inhabitants which geology has 
revealed. J 
I here take occasion to advert to the paper by Mr. Pattison, 
entitled, “ On the Chronology of Recent Geology” (read before 
the Institute on March 1, 1875), for the purpose of indicating 
the relation in which his treatment of that subject stands to the 
views maintained in the present paper. His method of dis- 
cussing the chronological question is that which I have above 
called “deductive,” as distingushed from the theoretical method 
which I have employed. He has, in fact, adopted the same 
deductive course of reasoning, and argued from the same 
premises, as Lyell, Dawkins, and other geologists, but, in my 
opinion, has, by sounder and more consistent arguments, success- 
fully combated the principles of their calculation of long geological 
periods. I am able to give my assent to tbe conclusions Mr. 
Pattison has arrived at on geological chronology, both because 
they are remarkably accordant with those I shall come to by a 
different route in the sequel of this essay, and because I cannot 
but regard this coincidence of the results from the two processes 
of reasoning as confirmatory of the truth of both. I revert 
now to what is mv special object, that of accounting for observed 
facts of geology by the physical theory already applied in 
explanation of the recorded facts of the Deluge. 
It is unnecessary for my purpose to enter into details 
respecting the evidences that have been discovered in modern 
times, of habitation of the earth by man during a long 
interval antecedent to the earliest date of profane history, 
this subject having been so well discussed by Sir John Lubbock, 
in his Pre-historic Times (3rd ed. 1872). One point, how- 
ever, requires to be specially noticed ; namely, tbe marked 
difference, as respects the character of the evidence, between 
the portions of that interval which have been named “neolithic” 
and “palaeolithic.” Not only the implements of the neo- 
lithic men exhibit more art and polish than those of the 
palaeolithic, the evidences also of habitation ■which they left be- 
hind, such as the Danish shell-mounds and the lake-dwellings 
of Switzerland, are found to be in situ, whereas the human 
remains and implements of the palaeolithic age, having been 
discovered almost exclusively in “river-drift” and “ caves,” 
VOL. x. G 
