W. M. Hudledon — Recent Wells in Dorset. 245 



of the upper beds by denudation or to less deposition within the area. 

 As might be expected, the Bagshots maintain their reputation as 

 a sandy series, but there is a certain amount of the usual clays, some 

 iron-stained, or mottled red, and some approaching the character of 

 pipeclay. Nos. 10 and 12 may to a certain extent represent the 

 famous Pipeclay horizon of the Creech district, and their position in 

 the series is not inconsistent with this supposition. There is a marked 

 change in the character of the sediments below ISTo. 15, which may 

 fairly be taken as the base of the Bagshots. In No. 16 we first 

 encounter the black flint pebbles so characteristic of a London Clay 

 horizon, but the Lower Tertiaries throughout the county are so 

 extremely uninteresting, both from an economic and a geological point 

 of view, that there is no need to dwell upon details beyond pointing 

 out that No. 25 probably represents the plastic clays in the lower part 

 of the Beading Beds which are much used for brickmaking in Dorset. 

 Owing to the method of boring it was not possible to ascertain 

 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 900 feet, 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 70 feet was reached, but the first 

 great supply was obtained a little below 400 feet, when the water- 

 level rose to within 96 feet of the surface. The artesian pressure, 

 therefore, was equal to raising a column of water nearly 200 feet into 

 the Tertiaries in addition to 70 feet 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 93 ft. 6 in. 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 75 feet above O.D. Moreover, in that direction the 

 protective cap of Lower Tertiaries soon fails (see Fig. 4). The main 

 water occurred between 675 feet and 685 feet. 



The borehole is situated about half a mile above Bovington Farm- 

 house 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 

 170 feet above O.D. The crest of the hill due north of this position 

 is about \\ miles distant, and there the Plateau - gravel attains an 

 elevation of 283 feet at the high end of Wool Heath. The nearest 

 outcrop of the Lower Tertiaries (London Clay and Beading Beds) is in 

 the Moreton plantations, 1-^- miles N.N.W., and the nearest outcrop of 

 the Chalk is about 2\ miles distant in the same direction (not in the 

 line of section). Along the line of section, north and south, 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 two 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 



