ARTESIAN WELLS IN DORSET AND ELSEWHERE. 193 



Owing to the method of boring it was not possible to ascer- 

 tain whether the Chalk is fossiliferous here, so that no question 

 as to horizon can be entertained. Assuming that the usual 

 thickness of the Chalk in Dorset is about 9ooft., the bottom of 

 the borehole is just half-way through that formation. There was 

 no supply of water in the topmost Chalk until a depth of yoft. 

 was reached, but the first great supply was obtained a little 

 below 40oft., when the water level rose to within 96ft. of the 

 surface. The artesian pressure, therefore, was equal to raising a 

 column of water nearly zooft. into the Tertiaries in addition to 

 7oft. of waterless Chalk. The War Office not being satisfied 

 with the Upper Water Supply, boring was continued, when 

 a lower and increased water supply was obtained, bringing up 

 the total to 60,000 gallons per day, and the water-level was 

 raised to 93ft. 6in. below the surface.* It should be noted here 

 that hydrostatic pressure may, to a certain extent, be reduced by 

 springs on the south side of the syncline, such as those outside 

 Wool, which are about 75ft. above O.D. Moreover, in that 

 direction the protective cap of Lower Tertiaries soon fails (see 

 Fig. 2). The main water occurred between 67 5ft. and 685ft, 

 which is some soft, lower than is indicated in Fig. i. 



Position of the Bovington Borehole (Figure 2). We may first 

 consider this from a topographical point of view and afterwards 

 study the geological position. The borehole is situated about 

 half-a-mile above Bovington Farmhouse on the west side of 

 the road which divides Bovington Heath from Wool Heath. 

 There is a patch of Plateau-gravel on the hillside, and it is 

 on this platform that the mouth of the borehole is situated 

 i7oft. above Ordnance Datum. The crest of the hill due north 



* The following is the size of piping used : 



Down to 20ft. .. .. I3in. 



132ft llin. 



180ft. .. .. lOin. 



250ft 8iin. 



726ft 7iin. 



