An interesting article by Bob Gillibrand has appeared recently on the Happy Wanderers club website, which is run by Mick Melvin (himself a former cave diver). Bob gives information about the somewhat extreme deplyment of the "Tadpole" bottles on Ken Pearce's 1960s expeditions, which are worth reading. There is also a link to a short modern video shot by French cave divers, in which they find one of Pearce's Tadpole bottles near the end of Sump 1. Bob's article is currently available from the site's home page here:  http://www.happywanderers.org.uk/