980 PROFESSOR J, PRESTWICH ON THE EVIDENCES OF A SUBMERGENCE 
Tliese reasons, although not conclusive, and requiring corroboration, afford some 
grounds for supposing that the submergence did not extend to Egypt. 
Conclusion. 
The seemingly confused accumulations of superficial debris, lying on the surface of 
the land without apparent order or stratification, led the early geologists to conclude 
that they were all due to the transient action of water and had a common origin, 
but the explanation wanted the necessary geological data and definition.* Subsequent 
research lias introduced order, and discovered agencies adequate to the explanation of 
most of the phenomena. Glacial, fluviatile, and meteoric action have claimed a large 
share of the work, and accounted for much which was then obscure. Nevertheless a 
residue, which supports to a certain extent the contention of the early geologists, 
remains, and which, as I have already explained, cannot be placed to the account of 
any of these agencies. It is to the various forms that this residue assumes, that 
I have applied the general term of “ Rubble-drift.” The reason why I have not 
retained the original term of “Diluvium,” is that this has been, and still is on the 
Continent, so widely applied to fluviatile, subaerial, and other drift beds, that it is 
desirable to avoid a term so variously used, whilst, at the same time, it does not 
embrace some of the more important phases of the Rubble-drift. 
I am well aware that several objections, more or less formidable, may be raised to 
the hypothesis which I have suggested to account for the origin of this drift. A few of 
these I may allude to here, though it would not be possible to discuss in these pages 
the wide and important general questions involved. Those who hold uniformitarian 
views will object to the want of known precedents and to the exceptional character 
of the agency proposed. In this difficulty I cannot share. I must repeat what I 
have long contended for,t that it is impossible to suppose that our very limited 
experience—say of 2000 years—could furnish us with standards applicable to the 
comparatively illimitable past. In fact, those that are relied on depend upon unstable 
conditions and are liable to vary with every passing century. While admitting the 
permanence of the laws of Nature, it is impossible, under the conditions through which 
this globe has passed, to suppose that at all former periods the effects, which have 
resulted from the operation of those laws, though equal in hind, were equal in degree. 
As in other similar questions, we must judge of the hypothesis not by an d priori 
* A very complete and valuable body of references to, and abstracts of, these early opinions vill be 
found in Sir Henry Howorth’s ‘ The Mammoth and the Flood,’ and in his various papers in the 
‘ Geol. Mag.’ for 1882. It must, however, be borne in mind that the larger proportion of the phenomena 
upon which those opinions were based have since been shown to be referable to glacial and fluviatile 
agencies, so that some of them are no longer applicable to the conditions as they were then interpreted. 
Sir Henry also adopts an hypothesis somewhat analogous to my own, but based on different grounds, 
and treated from a different point of view. It relates also to a different area. 
t ‘Inaugural Lecture,’ Oxford, p. 33, 1875. 
