CHAPTER VI - G.B. CAVE

Abstract

This chapter discusses the excavation of G.B. cave. The entrance to the cave is at the bottom of a vertical shaft excavated in a field some 200 yards south of Charterhouse. The existence of an extensive underground system in this area had been considered probable for many years from several surface indications. The impermeable limestone shales merge into the massive limestone, and it is therefore the first point at which water draining from the southern slopes of Blackdown can go underground. During the winter, the amount of water engulfed by Tyning's Swallet is considerable, the stream being fed by overflow springs issuing higher up the hillside at the junction of the old red sandstone and the limestone shales. After the excavation process started, gradually the shaft grew deeper until the excavated swallet was encountered, and it became apparent that the shaft was going through a definite water-worn opening in solid rock. The shaft was slowly deepened by a further 3 feet, when a floor of solid rock was reached. Running across it in line with the original swallet was a narrow fissure. Use of explosives finally revealed 1500 feet of cavern that extended downward to the water table some 500 feet below.