ARTESIAN WELLS IN DORSET AND ELSEWHERE. 195 



of this position is about i miles distant, and there the Plateau- 

 gravel attains an elevation of 2 8 3ft. at the high end of Wool 

 Heath. The nearest outcrop of the Lower Tertiaries (London 

 Clay and Reading Beds) is in the Moreton plantations, i miles 

 N.N.W., and the nearest outcrop of the Chalk is about i\ miles 

 distant in the same direction (not in the line of section). Along 

 the line of section, N. and S., the distance of the two outcrops 

 of Chalk, across the syncline, is a little under 4! miles, and this 

 gives the width of the Tertiary basin through Bovington. The 

 fact is that, previous to its final disappearance, about 2 miles 

 east of Dorchester, the Tertiary basin is very much narrowed in 

 the vicinity of Wool and Bovington owing to the northerly 

 advance of the Chalk on the south side of the synclinal. A 

 line drawn across the basin through Holme instead of through 

 Wool, shows a width of nearly nine miles, as against the 4^ miles 

 through Wool or Bovington. 



When we come to study the geological position of the 

 Bovington Borehole, the measurements of the Borehole section, 

 in conjunction with the surface plotting based upon the ascer- 

 tained contours, enable us to obtain a fairly accurate conception 

 of the prevailing conditions. The true axis of the tectonic * 

 syncline (see Fig. 2), can only be fixed approximately, but in this 

 case it probably almost coincides with the axis of the Frome 

 valley, which here runs very nearly in the trough of the syncline. 

 On the meridian of Worgret near Wareham, on the other hand, 

 the bed of the Frome lies a long way south of the synclinal 

 axis. Generally speaking, the southern limb of the Dorset 

 syncline is shorter, and, therefore, steeper than the northern 

 limb. In this case a northerly dip of 6 is assigned to the 

 south limb above Burton Cross, on the strength of dips 

 observed in the Chalk near Wool. According to statements 

 previously made in this paper, there is reason to believe that 

 the northern limb in the neighbourhood of the Borehole has a 



* " Tectonic," i.e., due to crust -movement, as distinguished from surf ace - 

 sculpture due to erosion, 



