50 
THE PRINCIPAL FLOOR. 
(No. 41). Red rocks of uncertain geological position have been 
found south of the Thames, at Crossness, at Streatham, and at 
Richmond. The deep boring at the Richmond water-works, 
described by Prof. Judd, passed, after piercing the Gault, 
through a small thickness of what are believed to be Neoeomian 
"beds, followed by about 87 feet of strata representing the Great 
Oolite, and then entered red sandstones and marls, similar to 
those so often found within the London area. 
Although specimens of the underground floor of ancient rocks 
Leneath the London Basin are those of most interest, there are 
other samples in this case showing cores from deep borings 
elsewhere, as at Stutton, near Ipswich ; at Swindon, and in 
Northamptonshire and Cheshire. 
Illustrations of the Sub-Wealden Exploration. 
Case JS T o. 19. 
On the occasion of the meeting of the British Association at 
Brighton in 1872, a bold geological experiment was projected by 
Mr. Henry Willett. The experiment consisted in an attempt to 
ascertain the thickness and order of succession of the several 
secondary rocks beneath the Wealden area in Sussex. For some 
years the notion had been gaining ground among geologists 
that these secondary rocks were comparatively thin in the 
south-east of England, and that some of them might be altogether 
absent, so that the older or palaeozoic rocks would probably be 
found within a moderate depth. The site finally selected for 
the enterprise was in the parish of Netherfield near Battle. 
After the boring had reached a depth of 1,030 feet an accident 
led to the abandonment of this hole, and a new boring was 
commenced with diamond-mounted drills on an adjacent spot. 
The second boring attained a depth of nearly 2,000 feet, when it 
was found necessary to suspend the work for lack of funds. 
The Case before us contains a geological model of the 
Wealden area, by the late Mr. W. Topley and Mr. J. B. Jordan. 
There are also a number of solid cores of rock drilled out by the 
horing tools : some of these were extracted by the old-fashioned 
tools employed at the commencement of the work, but most of 
them were obtained by the diamond-mounted drills. Some of 
these steel crowns, set with rough black diamond or carbonado 
(p. 103), are here exhibited; whilst the machinery employed at 
the surface is represented in the accompanying photographs. 
The borings were commenced in the Purbeck series, and valuable 
gypsum (p. 109) was discovered at a moderate depth ; this 
mineral is now worked commercially at Netherfield. A great 
thickness of Kimeridge clay was penetrated, much of which was 
found to be highly fossiliferous, and below the Kimeridge clay 
the borers reached beds of doubtful geological age, probably 
either Oxford clay or representatives of the Coralline Oolites. 
A large map showing the geological structure of the Wealden 
..area is suspended under the neighbouring Gallery. 
