ANNIVERSARY ADDRESS OF THE PRESIDENT. 41 
_ Leaving these remotest geological ages for later ones, the first 
paper that was read this session was an excellent example of the 
valuable kind of work which is peculiarly possible to a geologist 
whose long residence in a particular locality makes him thoroughly 
' familiar with all its physical circumstances, and enables him to seize 
each fresh exposure of rocks; and, which constitutes a great safe- 
guard against errors arising out of hasty observations, allows him to 
check first impressions by frequent visits. I allude to Mr. Walford’s 
paper “On the Relation of the so-called Northampton Sand of 
North Oxfordshire to the Clypeus-grit.” Its great value was abun- 
dantly testified in the debate which ensued on its reading, although 
some of the speakers did not conceal their doubts of the completeness 
of the demonstration attempted by the author. 
_ A communication by Prof. Sollas ‘‘On the Estuaries of the Severn 
and on their Tidal Sediment and Alluvial Flats” had, in addition to 
its intrinsic geological interest (one element in which was the de- 
monstration that these deposits comprise a larger amount of marine 
materials than had been previously supposed}, a very important 
bearing on sanitation in connexion with the disposal of the sewage 
of large towns. 
One of the latest stratigraphic papers, and one of very great 
Importance on account of the additional information it contained 
respecting the rocks beneath the metropolis, was that read on the 
6th inst. by Prof. Judd, entitled “On the Nature and Relations of 
the Jurassic Deposits which underlie London,” with an “Introductory 
Note on a deep Boring at Richmond, Surrey,” by Mr. Collett Homer- 
sham. Hxact measurements, then first obtained, of the thickness of 
the members of the Chalk, evidence of the separation of these by 
two junction-beds indicating unconformity (as Barrois had noticed in 
France), the demonstration of members of the “ Great Oolite,” and 
the presence in these beds of pebbles derived from the older crystal- 
line rocks, the occurrence of a red sandstone, referred by Prof. 
Judd with great probability to the Poikilitic series, and the distinct 
proof of the presence of anthracite in the form of derived fragments 
in the Oolitic series, rendered this paper the most valuable contri- 
bution which perhaps has yet been made to our knowledge of the 
sequence and behaviour of the rocks beneath London. 
Dynamical Geology was represented by Mr. H. J. Johnston Lavis’s 
paper “On the Geology of Monte Somma and Vesuvius, being a 
Study in Vulcanology ;” by Mr. D. Mackintosh’s communication, 
entitled “‘ Results of Observations on the Positions of Boulders and 
the Evidence they furnish of the Recency of the Close of the Glacial 
Period ;” by Mr. A. J. Jukes-Browne’s two communications ‘‘ On the 
relative Age of some Valleys in Lincolnshire,’ and ‘‘On some Post- 
glacial Ravines in the Chalk-Wolds of Lincolnshire,” and, lastly, by 
a paper from Mr. T. Mellard Reade, ‘On a Delta in Miniature: 
27. years’ work.” 
Whatever estimate may finally be formed of the precise value of 
Mr. Johnston Lavis’s communication in its bearings on the complex 
questions of vulcanology generally, no doubt can be entertained of 
