On the Mlanumoth at Cresiwell. 
By A. T. Metcatrs, F.G.S. 
MW HE bone-caves of Creswell have, during the last ten 
#} years, through the able exertions of the Rev. J. M. 
Mello, F.G.S., been subjected to a systematic explora- 
tion, and are now so well known to all interested in science that 
no general description of them need here be given. 
They are somewhat exceptional as regards the geological forma- 
tion in which they are found, not occurring in Carboniferous Lime- 
stone, but in Permian dolomite or Lower Magnesian Limestone. 
The Magnesian Limestone in England forms a very narrow tract of 
country extending from Durham to Notts. In the former county 
it has a thickness of 600 feet, but gradually thins southward, and 
dies out near Nottingham, at a point twenty miles south of Creswell. 
The lofty cliffs of Creswell, we know from other sections in the 
locality, must there represent the entire thickness of the formation. 
The picturesque ravine known as Creswell Crags probably owes 
its origin to the action of the little river Wollen which now runs 
through it. This statement will cause no surprise to anyone who 
is familiar with the mode of operation of denuding agencies in 
limestone districts. Going back into far antiquity, thé whole 
defile was, in all likelihood, one large cave excavated by the 
stream slowly eating its way along points of weakness in the rock. 
Some of the present caves are particle by particle losing their 
roofs, and their history in this respect is doubtless that of the 
