[ 102 ] 



XIII. On Artesian Wells near Silsoe in Bedfordshire. By Edward 

 J. Chapman, Professor of Mineralogy in University College, 

 London^. 



THE interest attacbed at the present time to all questions 

 connected with deep wells as a source of water-supply, 

 induces me to offer the following brief notice of a locality rich in 

 salient examples of this natm-e. I am not aware that any account 

 of this locality has hitherto been published ; no mention, at least, 

 is made of it in Mr. Prestwich's able and elaborate work on the 

 water-bearing strata around London, although in the immediate 

 vicinity of districts to which he has particularly referred. The 

 site in question was first pointed out to me by Mr. Homersham, 

 the engineer to the Loudon and Watford Spring-water Company, 

 with whom, in conjunction with" Professor Clark of Aberdeen, 

 and Mr. Suoulton of Dover, I first visited itf ; but I regret that 

 other duties have not allowed me to bestow that full attention 

 upon the locality that the interest of the subject demands. 



The village of Silsoe is situated on the inner edge of the outcrop 

 of the Lower Greensand formation — the higher division, or etage 

 Urgonienov Aptien of D^Orbigny — which at that point forms a 

 range of lowhills running parallel, or roughly so, to the great chalk 

 escarpment of Bedfordshire and the adjoining counties. Between 

 the two hill-ranges lies an undulating valley, having, a general 

 inclination towards the north-east, and possessing, in the parti- 

 cular locality here referred to, an average breadth of about three 

 miles. This valley consists of chalk-marl jjassing by almost in- 

 sensible gradations (through, it may be presumed, the upper 

 greensand equivalents) into gault J. The usual arenaceous cha- 

 racters of the upper greensand are, however, altogether undeve- 

 loped; and the true gault clay, lithologically speaking, is only 

 met with in isolated patches of small extent. One of these occurs 

 near Lower Gravenhurst, producing bricks of the well-known 

 light colour, combined with great uniformity of texture and with 

 great sectility. Gault bricks and tiles may, in fact, be cut 



* Communicated by the Author. 



t The existence of deep wells in this neighbourhood was, I believe, made 

 known to Mr. Homersham by Mr. George Edwards of St. Albans, at one 

 time a resident in the locality. The water was presumed to come from the 

 chalk ; more especially as the sui-face streams of the valley are actually 

 derived from that som-ce. Amongst other places at which the pha;nomenon 

 may be witnessed, a stream may be seen issuing from the chalk at " the 

 Bath," a picturesque spot about half a mile north of Barton Church. Slips 

 and faults on a large scale have evidently taken place along this portion of 

 the chalk escaqjment. 



X The transition of the gault into the calcareous clay may be traced more 

 particularly on the banks of the small stream-way near Ion Lodge, about a 

 quarter of a mile south-east of Wrest Park, 



