0:00:09 > 0:00:10This is Coast.
0:00:46 > 0:00:51Tide and traffic on the Thames flow two ways.
0:00:53 > 0:00:56In deep waters at the estuary mouth,
0:00:56 > 0:01:00ships from around the world come to unburden themselves
0:01:00 > 0:01:03on the docks at Sheerness.
0:01:04 > 0:01:06But back in the 19th century,
0:01:06 > 0:01:11a group of foreign stowaways snuck off a ship and never left.
0:01:11 > 0:01:16They set up a secret community within the harbour walls.
0:01:16 > 0:01:20This is the des res of Britain's only colony of scorpions.
0:01:24 > 0:01:26But not the monster kind.
0:01:28 > 0:01:32European yellowtail scorpions arrived here from Italy
0:01:32 > 0:01:35on a masonry ship some 200 years ago.
0:01:37 > 0:01:40Now the offspring of those Italian scorpions
0:01:40 > 0:01:42have found a British admirer.
0:01:45 > 0:01:48Hi, I'm Becks, and I'm a scorpaholic.
0:01:48 > 0:01:52I've been fascinated by scorpions since I was a teenager,
0:01:52 > 0:01:54and been hooked ever since.
0:01:54 > 0:01:58I'm here to see Britain's only colony of scorpions.
0:01:58 > 0:02:01I've got to wait for the sun to go down.
0:02:03 > 0:02:06Properly dark now, so I'm going to see if I can find some.
0:02:06 > 0:02:08I'm using a UV torch
0:02:08 > 0:02:11because scorpions glow under ultraviolet light.
0:02:11 > 0:02:13I think I've just spotted one.
0:02:14 > 0:02:15Definitely an adult.
0:02:15 > 0:02:18Probably out looking for something to eat.
0:02:18 > 0:02:21It is pretty cool, though, having scorpions in the UK.
0:02:23 > 0:02:25They are a member of the spider family.
0:02:25 > 0:02:27They've got eight legs, not six.
0:02:27 > 0:02:29They eat woodlouse,
0:02:29 > 0:02:32they're ambush predators so they will just sit and wait,
0:02:32 > 0:02:36and then something will come past and they'll jump out and grab it
0:02:36 > 0:02:38and subdue it with their claws, rather than stinging it.
0:02:38 > 0:02:44They don't generally use their stings, these ones.
0:02:44 > 0:02:46# That's amore! #
0:02:46 > 0:02:48Very happy that we found some.
0:02:48 > 0:02:50This is a tiny little incy one.
0:02:50 > 0:02:54So cute. With tinyness comes speed.
0:02:59 > 0:03:00It's been a great night.
0:03:00 > 0:03:03We've seen loads of scorpions,
0:03:03 > 0:03:07but I think I'll put this one back before it legs it.
0:03:07 > 0:03:10Bye, little fella.
0:03:11 > 0:03:15Yeah, I think I'll leg it now, too!
0:03:29 > 0:03:34I'm exploring the Firth of Forth on Scotland's east coast,
0:03:34 > 0:03:38where canny folk profited from their prime location,
0:03:38 > 0:03:41ideal for seaborne business.
0:03:41 > 0:03:47And with rich seams of coal for power, the population boomed.
0:03:47 > 0:03:49With more mouths to feed,
0:03:49 > 0:03:51getting enough fresh food was tricky
0:03:51 > 0:03:55so they looked to the sea to preserve their provisions.
0:03:57 > 0:04:01You'll find the evidence at St Monans.
0:04:05 > 0:04:10Here, food-processing created a curious landscape.
0:04:12 > 0:04:15The shore is lined with lots and lots
0:04:15 > 0:04:19of very strange grass-covered humps.
0:04:19 > 0:04:23What seems to be a ruined building over there,
0:04:23 > 0:04:26and up there a stone windmill.
0:04:28 > 0:04:32The ruins of industrial activity reveal themselves the more you look.
0:04:36 > 0:04:38This land was remodelled
0:04:38 > 0:04:42by people making the most of one bounty from the sea
0:04:42 > 0:04:44that isn't in short supply - salt.
0:04:46 > 0:04:50Before refrigeration, salt was a valuable commodity,
0:04:50 > 0:04:54preserving herring landed along the east coast.
0:04:55 > 0:04:58Scottish salt was also exported to England,
0:04:58 > 0:05:02turning a tasty profit to the saltworks.
0:05:04 > 0:05:07Those strange hummocks come in sets.
0:05:07 > 0:05:12Each set of hummocks is the ruins of a pan house.
0:05:12 > 0:05:14Inside each of those pan houses
0:05:14 > 0:05:17there was an iron pan about six metres by three metres
0:05:17 > 0:05:19with coal fires beneath it.
0:05:19 > 0:05:21Sea water was pumped,
0:05:21 > 0:05:24probably using this windmill from the sea, in pipes,
0:05:24 > 0:05:26up to each pan house.
0:05:26 > 0:05:29Once it had been boiled off in the pans, you had salt.
0:05:33 > 0:05:36A rare film brings the enterprise back to life.
0:05:38 > 0:05:43Saltworks once flourished along Scotland's east coast.
0:05:43 > 0:05:46The last operation at Prestonpans
0:05:46 > 0:05:49didn't close its doors until 1974.
0:05:52 > 0:05:56It was the abundance of coal along this estuary
0:05:56 > 0:05:58that made it a good site
0:05:58 > 0:06:00for boiling up sea water.
0:06:02 > 0:06:05A sample of sea water stirs up a mystery
0:06:05 > 0:06:09right at the heart of this forgotten industry.
0:06:10 > 0:06:13Out there is the sea full of salt.
0:06:15 > 0:06:17And I can certainly taste it.
0:06:17 > 0:06:20This little brook running into the sea...
0:06:22 > 0:06:25..doesn't taste salty at all,
0:06:25 > 0:06:32so why is fresh water fresh and why is sea water salty?
0:06:35 > 0:06:40It's one of those brilliantly simple, infuriating questions
0:06:40 > 0:06:42that kids ask.
0:06:42 > 0:06:45Why is the sea salty?
0:06:45 > 0:06:47I'm enlisting the help of a grown-up.
0:06:47 > 0:06:52Simon Boxall's from the National Oceanography Centre.
0:06:52 > 0:06:54He should be able to work it out.
0:06:54 > 0:06:57We've all swum in the sea, we know it doesn't taste like fresh water,
0:06:57 > 0:06:59Simon, but why is it salty?
0:06:59 > 0:07:02You have to go right back to the beginning stage of the Earth,
0:07:02 > 0:07:05back several billion years.
0:07:05 > 0:07:07If you go back that far, the Earth was a completely different place.
0:07:07 > 0:07:10It was full of volcanic eruptions,
0:07:10 > 0:07:11there was lots of steam around.
0:07:11 > 0:07:14But also there was a lot of sodium in the rocks,
0:07:14 > 0:07:17and that sodium was being hit by the hydrochloric acid
0:07:17 > 0:07:20that was given off by these volcanic vents.
0:07:20 > 0:07:22And then we take these two very harmful chemicals.
0:07:22 > 0:07:25On the one hand you've, got the element of sodium - very reactive.
0:07:25 > 0:07:27On the other hand, you've got chlorine -
0:07:27 > 0:07:28very dangerous and very reactive.
0:07:28 > 0:07:30You put the two together
0:07:30 > 0:07:32and you create something, sodium chloride,
0:07:32 > 0:07:35which is the sort of thing you sprinkle on your chips
0:07:35 > 0:07:36and certainly isn't harmful at all.
0:07:36 > 0:07:38So you've got this hydrochloric acid
0:07:38 > 0:07:40pouring out of the volcanic vents,
0:07:40 > 0:07:43meeting the sodium hydroxide which is already lying around
0:07:43 > 0:07:45- in the rocks on the seabed... - That's right.
0:07:45 > 0:07:49- ..creating this stuff called sodium chloride, which is salt.- Yeah.
0:07:49 > 0:07:52These ancient chemical reactions
0:07:52 > 0:07:54gave birth to our salty seas.
0:07:56 > 0:07:59We can create those sort of primordial days.
0:07:59 > 0:08:02We can actually take some hydrochloric acid,
0:08:02 > 0:08:04the sort of stuff that came out of the vents of the volcanoes.
0:08:04 > 0:08:06We've got some dilute sodium hydroxide,
0:08:06 > 0:08:08which represents the stuff that was in the rocks.
0:08:08 > 0:08:11And between us, if you want to, we can make some salt,
0:08:11 > 0:08:12we can take these two quite nasty chemicals
0:08:12 > 0:08:16and we can produce something that's really vital to life in many ways.
0:08:16 > 0:08:19This is hydrochloric acid. It's very dilute.
0:08:19 > 0:08:22We're going to pop it into this vessel here.
0:08:23 > 0:08:27OK. We're going to then add our sodium hydroxide.
0:08:27 > 0:08:29Now, at the moment,
0:08:29 > 0:08:31basically the sodium and the chlorine are combining
0:08:31 > 0:08:33and that's giving off heat.
0:08:33 > 0:08:35- Can you feel that? - It's warm, really warm.
0:08:35 > 0:08:38- Wow!- We've effectively neutralised that acid,
0:08:38 > 0:08:39that sodium hydroxide,
0:08:39 > 0:08:42and what we have in there now is basically water...
0:08:42 > 0:08:44- Yes.- And salt.
0:08:46 > 0:08:50We've compressed billions of years of the Earth's evolution
0:08:50 > 0:08:53to make a miniature ocean.
0:08:53 > 0:08:58Boiling off our DIY sea water leaves the prize ingredient.
0:09:00 > 0:09:04So here it is, our very own home-made salt.
0:09:05 > 0:09:09White crystals that washed wealth in from the sea
0:09:09 > 0:09:12to help feed an estuary.