Correspondence — B. Hobson. 383 



and mineral composition are similar to other members of the group. — 

 A. F. Hallimond: On Autunite. It is concluded that the Cornish 

 material is essentially different from the Autun mineral, and the 

 name bassetite is proposed for the former, the fundamental characters 

 of which are : oblique, /3 = 89° 17', a:b:c = 0*3473 : 1 : 0-3456 ; 

 forms 010, 110, 120, Oil, 111, 121, 121, 141, 101 ; twinning by 

 parallel growth of a and c axes, perfect cleavage parallel to 010, also 

 100, 001; yellow, transparent; biaxial, 2E = 110°; pleochroic, pale 

 to deep yellow; soluble in acids. 



o o :r:r:e s:e> o zcsr 3D ie :r>r o is . 



THE UNDEEGEOUND FLOW OF THE YOEKSHIEE DEE IN 

 DENTDALE. 



Sir, — On walking from Hawes Junction to Sedbergh on June 23 

 this year, after a prolonged period of drought, I found the bed of the 

 Dee quite dry for many hundreds of yards. The river flows over the 

 Great Scar Limestone, and its bed forms an interesting study. Over 

 long stretches the bare limestone was exposed, worn to a slippery 

 smoothness and devoid of any surface pebbles or boulders, except in 

 the numerous cylindrical pot-holes drilled by them, some of which 

 were as much as 10 feet in diameter. Miniature canons have been 

 cut through the limestone, and, as Dr. Strahan 1 remarks, "the 

 gradient of the river-bed frequently agrees with the inclination of 

 the strata, and in such cases the water slides for many yards over the 

 smooth surface of the same bedding plane." At intervals waterfalls 

 occur and the river plunges from a stratigraphically higher to a lower 

 limestone bed. This applies more particularly to the river course 

 between the mouth of Cowgill Eeck and the seventh milestone from 

 Sedbergh. On the other hand, long stretches occur where the solid 

 rock of the river-bed is completely hidden under a chaos of boulders 

 or shingle. At several points pools of water occurred owing to inflow 

 of tributary streams or springs. These pools were in some cases 

 without visible outlet. Where boulders filled the stream bed 

 immediately below the pool it is, of course, possible that the overflow 

 of the pool took place over the solid rock but beneath the boulders. 

 In other cases the only outlet for the pools must be subterranean. 

 At one place higher up stream than the seventh milestone an inflow 

 of several gallons per mimite joined the Dee on its left bank, gushing 

 out from a subterranean channel. 2 "Whether this water was the same 

 as that which disappeared higher up stream or not would be difficult 

 to ascertain without chemical tests. It seems, however, clear that 

 some of the water of the Dee follows a subterranean course, though it 

 does not necessarily follow that it rejoins the river lower down. The 

 underground course of the Dale Beck near Ingleborough is well 

 known, but, so far as I know, that of the Dee has not been previously 

 mentioned. 



B. Hobson. 



1 Geology of Country around Ingleborough (Mem. Geol. Surv.), 1890, p. 42. 

 • 1 have since seen an underground inflow on the right bank above Lea Yeat. 



