TATE : INTERMITTENT SPRING. 
187 
one peculiarity which distinguishes it from all those just 
cited. In all siphon springs — for it is to the action of a 
natural siphon, of course, that the intermittent discharge is to 
be attributed — in all such springs the flow of water stops 
suddenly, the moment that the water level in the subterra- 
nean reservoir sinks below the inner opening of the siphon- 
like fissure. But the water which issues from Cowden Hill 
diminishes in volume gradually, and its flow is not suddenly 
arrested, as is the case in the other examples given above. 
This exceptional behaviour is capable of two explanations : 
(1) The water may issue from near the base of a deep 
funnel-shaped natural reservoir, through a siphon whose 
bend is nearly on a level with its roof, in which case the flow 
will diminish gradually as the pressure of the superincumbent 
water is reduced ; or (2) there may exist, between the curve 
of the fissure and the final outlet at the surface, a shallow 
basin, lodging some portion of the water, which, after the 
siphon has suddenly ceased to act, may be gradually drained 
of its contents, thus masking the abruptness of the cessation. 
There are reasons for believing that the latter proposition 
represents the conditions under which the Cowden Hill 
spring is discharged. 
NOTES ON THE MIDLAND COALFIELD. BY ARNOLD LUPTON, 
MEM. INST. C.E., F.G.S. (INSTRUCTOR IN COAL-MINING AT 
THE YORKSHIRE COLLEGE). 
The Derbyshire Coalfield has been well explored, but the 
Geological Survey Department has not published maps on a 
larger scale than an inch to the mile, and, as far as the writer 
is aware, not of later date than 1855 ; and the information 
contained in the memoirs of the survey of this district is by 
no means as elaborate as that contained in the extremely 
interesting and valuable book lately published by Professor 
A. H. Green and the gentlemen of the Geological Department 
who aided him in his survey of the Yorkshire Coalfield. It 
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