98 DR. A. H. COX: REPORT ON MAGNETIC DISTURBANCES IN NORTHAMPTONSHIRE 
underlain by about 60 feet of red marls and dolomitic limestones belonging to the 
Permian system. 
In all the 1800 to 1900 feet of strata just described as occurring below the 
Marlstone there is no single bed that could give rise to any magnetic disturbance. 
3. The Deep-seated Geology. 
(d) The Distribution of the Coal Measures. 
The divisions last mentioned—the Permian, Bunter, and Waterstones—thin out 
and disappear one after another when followed south-eastwards from Nottingham, 
with the result that the Keuper Marls eventually come to rest directly and with 
strong unconformity upon older formations. 
Where the succession is most nearly complete the Permian is underlain by the 
Coal Measures, a thick series of shales, fireclays, coals, and sandstones, with numerous 
thin bands of clay-ironstones. 
The Measures themselves crop out west of Nottingham, forming the southern 
terminatioji of the “ visible ” portion of the Nottingham and Yorkshire coalfield. 
Eastwards from Nottingham they are everywhere concealed by newer rocks, but 
have been reached bj^deep borings, with the result that a great extension of the 
Coalfield has been proved to exist underground, forming what is known as the 
“ concealed coalfield.” 
W. E. 
OXTON KELHAM 
BOREHOLE BOREHOLE 
Details of the bores and references are given by Dr. Walcott Gibson in his 
account of this concealed coalfield t and in various other Memoirs of the Geolorrical 
o 
Survey.! It is sufficient here to mention the borings at Kelliam, near Newark, and 
I am indebted to Sir Aubrey Strahan for permission to copy (with slight modification) this 
section from “ The Search for New Coalfields in England,” ‘Lecture to the Royal Institution of Great 
Britain,’ March 17, 1916. 
t See footnote on p. 94 for list of Memoirs, 
