vadose development (formed above the water table), including continuing formation of the main streamway, and phreatic passages (formed below a latterly lowered water table). These resulted in very different types of passageway, with the phreatic tubes, since abandoned by much of the water, forming an undulating route, much of which is known as the ‘short round trip’. Only a handful of the 11 principal sumps thus far passed can be dived without dedicated equipment (free-dived). The length of cave between the sumps are known by the number of the sump at the end of the stretch; thus the stretch between the entrance and Sump 1 is known as Swildon's One, between Sumps 1 and 2 as Swildon's Two, and so on. Sump 4 can be reached without going through Sumps 1 to 3, via Tratman's Temple, Mud Sump, Fault Chamber and Blue Pencil Passage; parts of this route are extremely difficult. The connection between Swildon's Hole and Priddy Green Sink was the first major through route discovered on the Mendip Hills. Following a number of months of digging and blasting, the link was made in 1996 at the top of the Cowsh Avens Series, a climb above Sump 4. The water in the cave resurges in Wookey Hole Caves. This was first demonstrated (by pouring dye into the water) by Graham Balcombe and Jack Sheppard of the Cave Diving Group, who first passed Sumps 1 and 2 in the 1930s. See also Caves of the Mendip Hills References Bibliography External links Forty years in Swildon's Hole, a Laurie & Maurice film, Wessex Cave Club Caves of the Mendip Hills Limestone caves