334 



ANNUAL REPORT SMITHSONIAN INSTITUTION, 192 8 



yards from the outcrop of the rock (Barrett and Besterman, fig. 

 28, p. 95), so the drifts would be shallower than under the center, 

 and water flowing over the bed rock from the side would pass under 

 No. 2, and collect along the deeper line past the bores 1 and 3. 

 The position of the favorable line is fixed within comparatively 

 narrow limits by the fact that the rock is also marked as visible 

 at the southeastern corner of the field; the drainage from this 

 patch of drift to " the rocky valley " shown to the south must go 

 under the ground marked as " common " between the two exposures 

 of rock. As Stone walked over this ground he doubtless saw the 

 rock outcrops and the limits of the area of sand and gravel, which 

 alone would yield shallow supplies of water. A man experienced 



E^GDEB 8. — Bant'tt & Besterman'i 

 Figure 21 



Fit; 49 The Shanklin Experiment : Ssctscn 



FiGORB 9. — Greatwood Copse, Isle of Wight. Figure 

 49 of Barrett & Besterman 



in the search for water would have known that the line through 

 1 and 3 would have been the most promising, even if he had not 

 a mental vision of the water flowing off the bedrock and collecting 

 in the sand in the lower part of the drift-filled guUey. 



Another case quoted by Barrett and Besterman (1926, p. 208) as 

 " one of the best on record," was near Greatwood Copse at Shanklin 

 in the Isle of Wight. (Fig. 9.) The permeable Upper Greensand 

 there rests upon an impermeable clay, the Gault. The sandy beds 

 immediately above the Gault are naturally water-bearing. A double 

 well yielded about 4,000 gallons a day, and more was wanted. A 

 heading was then made through the sandstones on the advice of H. 

 Bristow of the Geological Survey, and it obtained from 9,000 to 

 18,000 gallons a day. Three other geologists, Topley, Norman, and 

 Sir Aubrey Strahan were subsequently consulted, but their proposals 

 were not carried out ; and Topley pointed out that the heading driven 

 in accordance with Bristow's advice was at too high a level. Mullins 



