Correspondence—Dr. H, H icks. | 47 
THE MAMMOTH AND THE FLOOD. 
We have received a somewhat lengthy communication from Mr. 
H. H. Howorth, M.P., in which he reminds us that so recently as 
1880 Sir Andrew Ramsay expressed the opinion that “from the 
Laurentian epoch down to the present day, all the physical events 
in the history of the earth have varied neither in kind nor in 
intensity from those of which we now have experience.” (Address 
to Geol. Section, Brit. Assoc., Swansea.) We are glad to be in 
sympathy with Mr. Howorth in his opposition to this doctrine, but 
we do not believe it is upheld by many geologists at the present 
day, nor is it taught in modern text-books. (See Geology, by A. H. 
Green, Ed. 3, 1882, pp. 694—696; Text-Book of Geology, by A. 
Geikie, Hd. 2, 1885, pp. 8, 178; Outlines of Geology, by James 
Geikie, 1886, p. 3.) 
Mr. Howorth contends that over the greater portion of the Harth’s 
surface there is no such denudation going on (or even possible) as 
that which has taken place in past times. We have not disputed 
the notion that excessive denudation may have taken place in former 
times, for instance, during the Glacial period. Mr. Howorth, how- 
ever, objects to the employment of the term Denudation to include 
the action of springs and rivers in carrying away the soluble 
constituents of rocks! We are aware that literally the term is 
inapplicable, but in nearly every geological work it is used to 
signify the removal of material from any portion of the land. Mr. 
Jukes-Browne has indeed suggested that the word Detrition be 
used in this sense in place of Denudation, but we are averse to the 
introduction of new names, when the old ones are sufficiently 
intelligible. In reference to this subject we may refer Mr. Howorth 
to a work by Mr. Mellard Reade on “Chemical Denudation in 
relation to Geological Time.” Epir. Grou. Mae. 
THE DIMETIAN OF ST DAVIDS. 
Sir,—Mr. Mellard Reade’s paper in the GroLoctcaL Magazine 
for December on the Dimetian of St. Davids contains such striking 
evidence of a want of acquaintance with the subject, and such hasty 
conclusions founded on erroneous observations, that I should not 
consider it necessary to reply to it, were it not that a definite piece 
of so-called evidence is given which may lead to some misapprehen- 
sion if not corrected. 
The piece of evidence which he gives to prove “that the rock is 
not in any sense Archean, but is post-Cambrian, and intrusive,” 
occurs in the following passage relating to the sections at Porthclais : 
‘‘ At a distance of about 50 feet north of this contact and embedded 
in the granite is a vein of green shale about 18 inches across and 
another about 10 feet nearer to the contact about six inches across. 
1 As Mr. Howorth reminds us in his letter that the more important issues raised 
by his Reviewer (see Grot. Mac. October 1887, p. 473) can only be properly 
discussed when his second volume appears, we are content to await the issue of that 
work— the limited space at our disposal not admitting of the publication of lengthy 
letters in reply to Reviews.—Epir. Gru. Maa. 
