ON THE GLACIAL DRIFT OF FURNESS, LANCASHIRE. 213 



simply melting zones in the heart of the glacier. Sometimes they 

 rest upon the rock surface under the boulder clay, at others they 

 alternate with it in more or less equal thickness throughout its 

 depth, and occasionally they are found lying next the surface-soil. 

 No doubt by being now, what they became then, passages for water, 

 they are constantly and gradually extending themselves into the hard 

 substance of the boulder clay. 



By obtaining rough sections of numerous well-sinkings in the 

 boulder clay, under the town of Ulverstone, a pretty accurate know- 

 ledge of these stratified beds is arrived at. They are known to the 

 sinker as waterbars, and are, I think, identical in character with 

 those seen in section on the moors, and in the Furness railway cut- 

 ting. They are often found dry : hence several are passed before 

 one containing water is reached. 



They are described as having an average dip or incline of one 

 quarter of an inch in five feet. The gravels lie between yellow sand- 

 bed?, which are smooth on their interior surfaces (i.e. the surfaces in 

 contact with the gravels) and very compact. The pebbles are chiefly 

 " bright -blue" (Silurian). Occasionally granite pebbles occur, and 

 have this peculiarity, that the beds containing them are seldom more 

 than two inches thick. The boulder clay is said to shade off gra- 

 dually in colour from the yellow sands to that of its own, which is 

 generally bluish, though occasionally other tints prevail. Under the 

 west of the town the boulder clay is so hard as to break the pick 

 point, is very dry, and free of gravel seams for a great depth. 



This interesting deposit occurs in patches on our hills, is spread 

 more thickly on our moors, descends next the rock-surface into the 

 vales, forms fine sections on our south-eastern shores, and declines 

 down under the marine stratified drift, at the southern end of the 

 promontory. 



At the Lindale moor iron mines, a good section of nearly half a 

 mile is displayed by the sinking of the ground since the removal of 

 the underlying ore. The following measurements were taken for me 

 in two places along this section : — 



Soil. ft. in. 



Boulder clay ....... 5 0 



Sand and gravel 2 6 



Boulder clay 3 0 



Soil. 



Boulder clay ..^ 60 



Sand and gravel 2 0 



Boulder clay 9 0 



There is a pretty general uniformity in the upper deposits through- 

 out the length, but in some parts the lower boulder clay attains a 

 much greater thickness. The gravels dip gently to the south-east. 

 . In long dry weather the laminated sands become inconspicuous ; but 

 here and there a red tinge pervades the series and denotes the occa- 

 sional presence of water charged with iron. The boulder clay here 



