Clever little detector/logger, Stuart! As mentioned earlier in the thread I've used OB method for many tests - had a few misfires now and again, but 90% happy with the method and have successfully repeated a test over a 3km drainage route, and most recently a 4km one. (a fluorometer would be...

Thanks, Stuart, I get you on all that. We have a reasonably fast moving stream I'd say in the order of 20-30cm/sec - at least as far as the eye can see (and in wet weather it can be heard rushing or falling further ahead), so I'd say a fairly quick flow-through time is to be expected. To be...

I wonder what quantities you were injecting to turn both small (Barbon Beck) and medium (Dee) size rivers green! Last night I introduced a 100ml concentration of fluorescein (about 4-5g of powder) at the downstream limit of a cave to test a putative distance of under 100m to another nearby...

The 'detectors' will be people looking for it! ;) Yeah, I know I could put swabs in (have always done that with OBA), but then it's another trip to collect them etc. etc. In this scenario, we just want a quick visual on the evening: either they see it or they don't.

Thanks for confirmation (y) If I make up a solution, should it be released into the stream slowly?....so as to 'string out' the plume? Or do you just tip it in and let the stream do the work? I'm only thinking that perhaps a short plume has a greater chance of being missed by observers. The...

Thanks everyone for all your suggestions....and hilarious stories/anecdotes! - it sure is a substance to be reckoned with! Stuart France - thanks for the detailed response. I'm quite familiar with using OBA and have done many tests using the cotton wool and UV light method - many of these...

Many thanks for the link, Ian (y)

Can anyone recommend a good supplier/source of liquid fluorescein dye (or perhaps pwder if that is the preferred format these days? There's a lot of stuff online, but much of it looks like 'drain tester' stuff which I doubt is the real mccoy.

I think he might mean Penguin Hall...which is the short pitch after the free-hanging 3rd pitch, at a convergence of several avens. And thanks for the fine accolade you've awarded it! We enjoyed exploring it. It's certainly a novel hole with interesting situations. A shame it never hit that...

Great write-up, Tim, it all comes flooding back! ;) Looking forward to the next episode! p.s. I tend to agree that digging the lower cave might be worth a go, it was quite tempting at the time!

!WARNING! Erosion of the stream bank just downstream of the entrance to Aygill Caverns (near Bull Pot Farm) has drastically altered the local hydrology of Aygill, with serious consequences for access to the cave. The gill has been steadily eating away at the bank for several years now, but...

Just so you know..... A midweek trip into Aygill revealed the absence of the fixed rope on the first pitch, often known as the Traverse Pitch. The fixed rope allowed you to 'traverse' the pitch with just cowstails to protect a step across onto a ledge and boulder, from where there was an easy...

Whilst browsing a geography site for some other info, I noticed an interesting blog entry (on the same site) about a long river cave on the island of Palawan in the Philippines: http://basementgeographer.com/puerto-princesa-subterranean-river/ The basic facts, of a 24km long cave system with...

Anyone know how to get the contacts strip out of the bottom of the Duo battery case?  My cable's worn quite close to the exit port from the battery case and I could do with replacing it...but the contacts strip will have to come out. Are they know to be 'releasable'?...or will brute force and...

Anyone visiting Aygill Caverns should be aware that the tube crawl from the bottom of the Traverse Pitch (or 1st pitch) to the 2nd pitch now carries substantially more water than it used to and may flood in wet conditions. We have been working in Aygill on and off for several years and have...