Rob and Julian noticed a new choke down near Earthworm Passage in Magnetometer Pot on a diving trip. Coming from the Whale it is situated at the end of the rift you can stand up in where the passage to Earthworm leads off to the right. They pulled a few boulders out until a stream could be heard and a continuing passage could be seen.
The next trip down was armed with some digging gear and rope to pull away the more precarious boulders. Unfortunately the worst didn't move and those that did had a knack of only falling when someone was standing underneath them. The way on is a climb up through the choke following the stream that flows through the boulders. Here the passage rises to standing room. To the left a small inlet passage leads off, starting at stooping height but rising as the stream cuts into the mud banks. It stops after 150ft in a solid calcited choke. Back at the main passage a stream runs in the floor with banks of mud on the right. The stream comes out of a choke which is bypassed to the right. Above this is a muddy chamber. On the right is a solid wall, at the foot of which is a very low bedding plane the other side of which is thought to be Earthworm Passage. In the chamber under the left hand wall are two choked pools, probably connected to the stream leading to the original choke at the start of the dig. Above these pools is a short thrutch through more boulders. Here the passage drops down to a hole leading to a 20 foot hands and knees crawl.
The next trip by Rob and Julian was to investigate the different pools in the extension. All of them were found to be choked. Abandoning their bottles they continued to the muddy crawl. This changes from hands and knees to an incredibly muddy body sized tube for 30 feet - you stick to every wall. The tube ended at the top of a pitch for which they had no ladder.
That evening Julian caught Ben in an enthusiastic mood ie. in the pub, and persuaded him he wanted to go caving the next day. Taking a ladder for the pitch at the end of the tube, a bolt was put in the wall as there is no natural belay. The take off is rather awkward especially for those with long legs as the tube extends right up to the head of the pitch. 15 feet down lands in a foot deep pool of water seemingly with no way on. Unfortunately a very narrow crack of air provides the way on through a sporting duck under the wall opposite the tube. It emerges in a flat out crawl. A small passage was noticed just after this on the right but the route followed was straight ahead to where the roof rises slightly only to find the passage is blocked by stal. Some time was spent digging at this until it was discovered one could squeeze through. Assuring Ben he'd never get through, Julian disappeared into the continuing passage. After twenty feet a stream was met and downstream the passage was blocked again by stal. Upstream the passage continued for some 250 feet ending in a choke. On the way back a junction with a dry passage was explored. A crawl emerged in a rather large phreatic passage, but remembering his assistant lying in a pool of water back at the stal Julian returned.
A team of four returned to survey and finish the exploration. The small passage just after the duck was followed rather than the straight ahead route, and this bypassed the stal blockage. Downstream the passage was found to end in an unpleasant sump. Upstream the dry crawl was followed to a 15x20 foot phreatic passage ending abruply after 40 feet. The passage turned sharply left down to a sump with a mud and boulder slope preventing further progress. Two people were left to look at any loose ends while the others went out surveying only to find that they possessed a very erratic compass. Reaching the 15 foot pitch, what had been a small trickle had now turned into a torrent. However the duck in the pool at the bottom of the pitch remained passable which suggests that the pool must drain somewhere. Though many of the passages at the bottom of Magnetometer undoubtedly do fill up with water, many trips have been undertaken when the weather is extremely wet. On this trip water was flowing over the boulders at the start of the extension rather than just through them, but there was no noticeable increase in water level throughout the rest of the cave.
Surveying trips down Magnetometer seem to be bedevilled with bad luck: one trip to survey some new passage in Cow Close was curtailed by a distinctly nasty medical complaint; trips to Earthworm extensions were foiled once by an erratic compass and on another occasion by a boulder falling out of the roof at the start of the greasy tube onto someone's hand. Since then however the survey has been completed with no more excitement than a multiple light failure.
The total length of 700 to 800 feet of new passage with five new sumps and three new streams adds to the interesting and complex nature of Magnetometer breaking into some large phreatic passage, though intersected by some extremely sordid sections. It is an area that deserves further attention, heading as it does towards Penyghent.
Ben van Millingen