144 BULLETIN OF THE NATURAL HISTORY SOCIETY. 



The artesian wells have been grouped into three sets, each of which 

 has peculiar characters. Of these the first are those which penetrate 

 the surface deposits only ; the second are bored in the soft yielding 

 sandstones of the Coal Measures ; and the third penetrate Lower Car- 

 boniferous rocks of more varied nature, some of which have saline 

 waters of marine origin, now held in soft red and brown shales, and 

 sandstones. 



The three wells of the first group are typical of the varieties of 

 deposit which are likely to be met with in shallower wells. In Dr. 

 Berryman's well we have the full series of the surface deposits which 

 it is necessary to penetrate in order to reach the porous stratum con- 

 taining pure water. The upper deposit here is the mud of a salt marsh 

 forming an impervious covering to a porous stratum of sand, etc., of a 

 seashore or estuary origin (Macoma sand), and therefore likely to give a 

 decidedly brackish water. Beneath these sands there is a heavy bed 

 of clay " brick clay " (Led a clay), which serves to hold in the water of 

 the lower level ; this water is contained in a porous stratum of sand and 

 gravel beneath the clay. At this well the gravels are thought by the 

 owner to rest on the rock, so that a still older part of the surface 

 deposits, consisting of a confused mixture of clay, sand, and stones 

 (" Boulder clay "), usually cemented into a hard, compact mass, is 

 probably wanting at this particular spot, having been washed away 

 by the current that laid down the gravel. 



Of the well at St. Stephen we have less special knowledge ; it is 

 said to be situated on a ridge of land between two streams and pene- 

 trates only the brick clay. To have obtained water, however, the 

 porous gravels below must have been reached. 



Ready's well, in Fairville, is driven through a still more limited 

 range of the surface deposits, for at this point the lower gravels swell 

 out into a great ridge, with the brick clays resting on either flank, 

 but not covering it. This well is driven in the gravels only (unless it 

 may strike Boulder clay in its lower part) and the supply of water is 

 drawn from the gravels alone, by direct gravitation, and does not 

 necessarily come from a distance. 



The second group of wells may also be regarded as artesian ; they 

 are bored in the sandstones of the coal incisures which are "free- 

 stone"* and occasionally alternate with beds of shale, which would 

 serve as an impervious covering to the several masses of sandstone In 



Sandstones thai arc easily oul with the chisel, 



