17 
The Hon. Secretary reported the number of members of the section 
the same as last year, 23. The Secretary also read a list of papers con- 
tributed, and walks taken during the year, and stated that the Geological 
Magazine had been regularly circulated. 
Mr. Gillford exhibited some fossils from the lias for naming. 
There being only a few members present, Mr. C. F. Ravis's Paper on 
" Denudation in the Bristol District," was postponed to the next meeting 
of the Section. 
February 27th, 1868. — The minutes of the preceding meeting 
having been read and confirmed, 
Mr. C. F. Ravis read his Paper on " Denudation in the Bristol District," 
which had been postponed at the last meeting. After some preliminary 
remarks, the author went on to say — Two chief principles in the theory of 
denudation have been laid down. The first some years ago by Sir Charles 
Lyell, — namely, that the amount of waste of previously existing rocks is 
exactly equal to that of the deposition of new strata. 
A good illustration of this principle in our own neighbourhood is pre- 
sented by the condition of things at Aust Cliff. The beach there is 
strewn with large masses of stone which have fallen from time to time 
from the cliff. These masses are in process of formation into a bed of 
conglomerate, which will one day, unless the stones be removed by human 
agency, constitute a distinct stratum, extending as far into the bed of the 
Severn as the action of the waves is capable of conveying the stony frag- 
ments. 
Such a conglomerate would be made up of red marie, blocks of the 
"Bone Bed," masses of the ostrea and other molluscan beds, fragments 
of gypsum, and the other substances now composing Aust Cliff. In the 
meantime the cliff is wasting away by the combined action of the sea at 
its base, and the atmosphere, with its various agencies, on the upper por- 
tions, so that the denudation of the old strata keeps pace with the deposition 
of the new. 
The other principle of denudation is that which is so clearly and ably 
laid down by Professor Ramsay in his article on the subject, in " The 
Memoirs of the Geological Society," vol. I. The object of this principle 
is to determine the probable amount of waste to which the older strata 
have been subjected, by restoring in section the rocks as they formerly 
existed above the present surface. 
After insisting on the necessity of having sections of the existing rocks 
constructed on a true scale, the Professor explains that the depth to which 
