IN THE PLEASLEY AND TEVEKSALL COLLIERIES. 437 



that these " Wash-outs " may be due to quite different kinds 

 of aqueous action : — first, as in Durham and elsewhere, by a current 

 flowing at a high rate of speed in one direction, denuding and carrying 

 away the whole of the denuded material ; and secondly, as in the 

 Derbyshire " Wash," by a series of inundations or overflows of water, 

 each in-rush denuding a certain amount, and on subsiding depositing 

 part of the material at a higher level, whilst the remainder was 

 carried away in suspension. Such action may have been the result 

 of the periodical overflowing of a lake, or the more regular rise and 

 fall of water in an arm of the sea. At the time this action took 

 place the surface would doubtless be a soft, pulpy mass of vegeta- 

 tion in a state of decomposition, which would easily be removed by 

 a current of water, however slight. 



A " Wash-out " similar to the one described in these notes has 

 been met with in the Blackwell and other collieries, and described 

 in a paper read by Mr. G. E. Coke before the Chesterfield and 

 Midland Institute of Mining Engineers. This " Wash " has been 

 proved by the Blackwell coal-workings to run within 2^ miles south- 

 west of the Teversall pits (see the plan, fig. 1), and an impression 

 seems to exist in the minds of several interested in the subject, that 

 the Teversall and Pleasley "Wash" is a portion or continuation of 

 that at Blackwell, &c. The writer submits that this cannot be so ; 

 for, whereas the Teversall " Wash " is found in the Top Hard-Seam, 

 that at Blackwell has been proved in the Deep Hard Coal, some 200 

 yards below ; and as the Deep Soft and other coal-seams lying 

 between the Deep Hard and Top Hard have not been influenced by 

 either " Wash," it seems certain that they must have occurred at 

 vastly different periods : — the Blackwell " Wash " after the deposi- 

 tion of the Deep Hard Coal, but before that of the Deep Soft ; and 

 the Teversall and Pleasley " "Wash " at a very much later period. 

 viz., after the formation of the Top Hard Seam. 



Q.J.G.S. No. 183. 2r 



