1862.] HODGSON TJLVERSTON. 25 



to be*, is close to the steep side of the Gill, and is now strongly 

 fenced off. The Gill here may be from 14 to 16 feet deep; it is 

 thickly wooded. 



A division of the stream has lately found another entrance about 

 a quarter of a mile higher up. Here it filters through, leaving its 

 sediment on the surface, and forming mud-banksf, through which 

 the water noiselessly escapes in numerous little eddies. As in the 

 former instance, the engulfed stream is believed to take an easterly 

 direction. The Poaka Beck rises by several deep springs on Mean 

 Moor, about two miles to the north of Lindale Moor, at an elevation 

 of nearly 1000 feet. Taking rather a south-westerly course, it 

 runs nearly parallel with the vale of Lindale, separated from it by a 

 line of hills, but at no point of divergence exceeding the distance of 

 one mile. 



The superior claim of this stream, in regard to the deposit, over 

 the waters before noticed is, I think, obvious. Its longer course, of 

 nearly four miles from the rise to the fall, through a tract of varied 

 country, its thickly wooded banks and gills, its far greater body of 

 water (which in heavy rains is said to be almost white with mud 

 and clay from the higher grounds), and especially the remarkable 

 coincidence of its having been stopped from entering the ground for 

 the last twenty years, thus leaving time for the deposit to become 

 drained, are facts which seem to point to the Poaka Beck as the 

 direct cause of the deposit. 



Wherever water is precipitated into the earth through a chasm, it 

 must take along with it an amount of deposit proportionate to its 

 volume ; and, supposing that such engulfed water may afterwards 

 escape from the fractured rocks into the adjacent strata, thither it 

 will carry its mud, &c, especially if in the adjacent strata it find a 

 vacuity to receive it. 



Sir Charles Lyell, in treating of the phenomena of springs +, gives 

 some extracts from M. Hericart de Thury, and the * Bulletin de la 

 Societe Geologique de France,' which bear upon this subject. 



Although the rocks in Inman Gill are now near the surface, and 

 the Swallow-hole has been an open rock-chasm for the last sixty 

 years, the bed of the stream at one time would be higher, and the 

 gill not so deep. Therefore, however open or cavernous the subter- 

 ranean region between the Beck and the present seat of the deposit 

 might be, it is probable that the first influx was by infiltration, as 

 at present. One is led to this conclusion by the nature of the bluish 

 clay found underneath the vegetable deposit ; this clay, from the 

 scarceness of any vegetable forms, even in portions lying in close 

 proximity to the vegetable deposit, may be supposed to have been 

 collected by filtrated waters on their passage through the various 

 materials of that region, and so left on the floors of the cavities, indi- 



* From the point where I stood ; the stream passing between prevented my 

 getting close to it. 



t See Specimen, in the collection of the Society, with probably an alder-leaf 

 imbedded. 



j Principles of Geology, fifth edition, vol. i. p. 306. 



