the Strata betwee7i the Chalk and Wealden near Hythc. 309 



ruins of the superior beds, and their existence was until now un- 

 known." The author therefore could not attain his purpose without 

 having recourse to boring and levelling ; the mode of conducting 

 which processes, and the calculations connected with them, he has 

 explained. 



1 . The upper greensand was found to be entirely wanting on the 

 principal line of the section, the only trace of it being some grains 

 of sand mixed with chalk-marl over the gault. A second boring, 

 about half a mile eastward of the principal line, gave the same 

 negative result ; but at Folkstone Cliff, six miles distant, there is, 

 in a corresponding place, a true greensand, 15 feet thick, indurated 

 to the condition of stone, with much pyrites, and passing gradually 

 upwards into the chalk-marl through a thickness of 17 feet more. 

 The junction between the upper greensand and the top of the gault 

 below is decided and abrupt. 



2. The borings through the Gault, at its lower part, were unat- 

 tended with difficulty, and the limit between it and the lower green- 

 sand was very well defined. 



3. Lower greensand. — a. The uppermost division of this group, 

 rising and running out beyond the bottom of gault, disclosed a sur- 

 face inclined at the same angle, and continuous with that beneath 

 the clay, which appeared to have been removed by denudation. The 

 beds of this upper division are enumerated in detail, and the places 

 of some of the fossils specified. 



b. The Saltwood tunnel being driven directly through the upper 

 part of the middle division of the lower greensand, this portion of the 

 series became an object of great interest to the author, and is fully 

 described. In one boring, after ten feet of somewhat sandy yellow 

 clay, came a very dark green, tough and adhesive mass, almost black 

 when first brought to the surface, and containing very little sand. 

 This, which the author calls clay, he considers as the chief character- 

 istic of the middle division. At a depth of 53 feet sand was mixed 

 with it ; and at 56 feet a " rock" of limestone was reached, which the 

 author regards as commencing the next lower division of this group. 



c. The thickness of the third (or " quarry-stone ") division of the 

 lower greensand was ascertained by combining the results of several 

 different borings. At this period the author was induced, by a com- 

 munication with Dr. Fitton, to change the boring for a shaft, in 

 order to bring up more extensively, and to preserve, the fossils of the 

 unknown strata between the quarries and the Weald clay. This 

 shaft was 5 feet by 4 in dimensions, and it was found necessary to 

 support it throughout with timber. The strata thus cut through may 

 be considered, in a general view, as consisting of clay, which was 

 found to be 49 ft. 6 in. thick : and the bottom of this clay was sepa- 

 rated from the uppermost beds of the Wealden, containing the usual 

 freshwater fossils, by a layer of soft sand only one inch in thick- 

 ness. 



§ The measures of the several groups between the chalk and the 

 Weald clay, thus ultimately obtained, were as follows ; the general 

 dip being due north, at an angle of about 1° 19'. 



