Depth:137m Length: 1520.5m

Equipment Required:- l0ft ladder, 20ft ladder, l0m rope, 2 tapes

Care should be taken when entering this section of the B4-BS system as the entrance becomes water-filled after heavy rain and may remain blocked for some time. Foul air is always present in the lower sections of the Extension but

can be as high as the streamway in Largest Chamber or even the Rat Run when water seals the entrance.

The start of the B4-S Extension is found in Junction Chamber. The B4-5 system continues as low passage known as the Rat Run. The passage, 2.5m wide and l-l.5m high, continues for 65m where Coffin Chamber is reached. This chamber appears to be developed along a rift, possibly an eroded dyke. Coffin Chamber is l5m long, 5m high and 3-4m wide and contains some aragonite. Apart from one large block of rock the floor is rubble. At the far end of the Chamber under a slab of rock is a l.5m deep hole in the floor which is the way on.

The cave continues for 27m as tight broad flattener, 2m wide and 0.25-0.5m high to a small chamber 2m high. A further 43m leads to the Traditional Resting Place, a chamber up to 5m wide with a decorated side passage 1 Om long. 22m on, a 7m high aven is reached. Here the passage is 2m wide and 2m high but constricted by flowstone

at one point. Another aven, 1 2.6m high, is reached after 30m. The passages becomes low again for a short distance then increases in height for 90m to the B 15 junction on the left.

The cave continues along the streainway for 1 7m to a 3m drop. A handline may be used but a I Oft ladder is recommended for this exposed overhung climb. The passage overhead leads back into Largest Chamber. At the bottom of the climb are vertically bedded, non-calcareous micaceous sandstones and shales which are part of a turbidite sequence within the limestone. This passage, 5m wide and 8m high enters the Ribbon Room after lOin where the roof lowers to 6m. A streambed enters on the left hand side. On the right hand side is a hole in the rubble that would take water into lower passages which reconnect with the main passage further down the cave. The roof and up to the right in the Ribbon Room is well decorated.

The boulder and rubble floor continues down a 5m climb to the start of the Upsidedown Rowboat Tunnel. I 2m from this climb is a low passage on the right which loops to the lower streamway. The Upsidedown Rowboat Tunnel is 2-4m wide and 2.5-3m high with a flat roof. A floor canyon is developed near the end of the Tunnel where the loop reconnects with the main passage. The high level passage on the left is 75m long with two connections to the lower level. The way on is down the 3m climb followed by a steep climb down bedrock for 12m to the lower level. This low wet nasty crawl ends in the Lavatory Pan Squeeze. Skinny agile cavers can avoid paddling in the puddle by taking the overpass. The Lavatory Pan is followed by another squeeze through a hole O.25m wide and 0.3m high which drops down 1 .3m to a ledge at the top of a 6.5m pitch which requires a 30ft ladder.

From the bottom of the pitch, the rift ends in a low crawl with a gravel floor. The side passage on the right is tight and awkward and ends after 40m. The way on continues as low passage l.2m high and 2-2.5m wide for 1 8m to where a floor canyon has developed. The roof rises to 8m and the serpentinious passage becomes narrow in what is called The Serpent. After 60m The Baby Snake is reached via a low awkward squeeze followed by a 1 .4m climb, To the right is a squeeze up a sediment slope that leads to an aven which can also be reached high on the right hand wall in The Serpent.

To the left a very narrow awkward climb up a floor canyon leads to 35m of passage with an active stream and ending in a long pool which meets the roof. To the right is The Large Snake and the way on. At its beginning The Large Snake is 2.5m high but the roof lowers gradually. After 25m shallow water is encountered. The passage continues for 1 5m to The Swim which can be negotiated by duck waddling through the dark sulphurous water. The Swim is 2.5m wide, 1 .3m high and 35m in length with a minimum air space of

0.3m at the time of surveying. 15m of low crawl leads to the Why Junction.

The Why Junction is 3.5m wide and 4m high. Luxury! The canyon to the left reduces in size after 25m and continues as narrow passage which ends after 40m. Straight ahead from the Why Junction is 65m of walk-through passage. A short climb followed by a steep slippery slope up to the left leads to a chamber similar to Largest Chamber. This has not been fully explored due to the treacherous slope. At the bottom of the climb to the right is a duck under O.8m high which leads to St Patricks Lake Chamber, 25m long and 5m high. On the left is a sloping mud floor and on the right is St Patricks Lake which is black and orange from bacterial activity.