REV. E. HILL ON WKLLS 1\ WEST SUFFOLK BOULDER-CLAY. 5Si3 



34. Oil Wells in Wr.sr Sufp'olk Bouldeu-clvy. By the Rev. 

 Edwin Hill, ^[.A., F.G.S. (Read June 24, 1801.) 



On taking up my residence in the heart of the Suffolk Boulder-clay, 

 1 at once began to enquire the depths of wells, in order to learn the 

 thickness of its mass. The nature of the answers was unexpected. 

 The depths at which water is obtained appeared altogether irregular 

 and capricious ; ultimately it seemed necessary to conclude that in 

 some cases, possibly in many, the water is met with not below but 

 in the interior of the Clay itself. 



Here is an instance. A well in an outhouse of this Rectory 

 (Cocktield, seven miles S.S.E. of Bury St. Edmund's) gives water at 

 a depth of 35 feet. Another, outside its grounds, 120 yards W., 

 is 74 feet deep, and I am told that in sinking it no water was 

 obtained till this depth was reached. But another, the same 

 distance jS'.JiS'.W. of the first, is only some 8 or 10 feet in depth. 

 Boulder-clay forms the subsoil to within a few inches of the surface, 

 which in the case of each of these wells is about 300 feet above 

 Ordnance datum. 



Other wells have the following depths, the distances and directions 

 being measured from the Rectory : — One half a mile N.N.E. (surface 

 about 290 feet) * 50 feet ; another a quarter of a mile ^. (300 feet) 

 70 feet. In the opposite direction, at Cockfield New Hall, three 

 quarters of a mile S. W. (255 feet), water was found at various depths 

 down to 35 feet, but at the New Barn, a quarter of a mile farther 

 S.W. (about 280 feet), the depth was 126 feet. At the Post Office, 

 about a mile W.N.W. of the Rectory (about 270 feet), a shaft was 

 sunk 83 feet and abandoned, nothing beyond surface-water having 

 been obtained, while a few hundred yards off in several directions 

 supplies are furnished by wells of varying but moderate depths. 



It may be asked whether these irregular depths may not be due 

 to the irregular surface upon which the Clay is lying. But the 

 water-levels in the three wells first named, so near, yet of such 

 different depths, appear to have no connexion. Again, such an 

 irregular subsurface must certainly be intersected by any long 

 trench if of any serious depth. Such a trench exists in the valley 

 of a brook which runs from N. to S., passing about half a mile west 

 of the Rectory, and more than 70 feet below the levels there. 

 This valley taps a few springs, and here and there in the bed of 

 the brook a little gravel may be seen. But nowhere do I see any 

 indication that it has reached an extensive underlying formation. 

 The conclusion I come to is, that the water must be contained in 

 permeable seams, included in the mass of the Boulder-clay. 



The I lay itself appears absolutely impervious to moisture. In 

 a neighbouring field water stood for several weeks in a small 

 I)it by the side of a deeper trench not two feet off. A shallow 

 ditch recently dug along a fence a few inches into the Clay lay 



* Kuiiibers between parentheses indicate height o^ surface above sea-level. 



