Bartimaeus

We returned to Trevor at the north end of the Pontcysyllte Aqueduct with an important mission - to get the waste tank emptied.  The hire base here is extremely busy on change-over days - Friday to Monday - but we hoped to be able to get their attention, and access to the wharf by turning up on a Thursday afternoon.  That all went very smoothly, it was even slightly cheaper than the self-service units we often use.

Clare had assumed that we would press on over the aqueduct again, but I had spotted an alternative.  We'd turned towards the aqueduct as we arrived so that we were conveniently placed for the pump out.  Behind us now, under a low bridge, was the dead-end arm of the canal that leads to the Trevor Basin.  This was once a busy wharf for industries that grew up around the canal.  Originally it was intended that the canal would go this way to Chester, but that section of canal was never built.  It seems incredible that the aqueduct, which took ten years to build, was in the easy part of the project.

I'd spotted what I thought was a suitable mooring.  While we were trying to work out how to moor up, a new neighbour happened by and pointed out that we were at a winding spot.  It didn't really look like one because it was part of a fork in the basin, but once he'd pointed it out he was obviously right.  He suggested we'd be better off the other side of his boat, right at the end of the canal.  There isn't quite as much open sky as I'd like, but it was a good choice nevertheless.

I took myself off to explore the aqueduct again on foot.  It was a lot quieter than our previous visit, so I was able to linger and notice things I hadn't seen before.  Now and again there were signs of ageing - a broken piece of metal or a repair.  For a structure that is 220 years old, it is in remarkable shape.

In the morning, we waited until the rain wasn't too heavy before walking the short distance to the Visitor Centre to see what more we could learn.  By now I had seen that the trough is made up of large cast-iron pieces held together with nuts and bolts.  We now learned that the sealant between the plates was a mix of sheep's wool and lead, dipped in molten sugar before application.  This was then sealed with bitumen.

At the major service just before the bi-centenary, much of this sealant was still doing its job satisfactorily.  A number of the nuts and bolts were replaced by replicas made using reclaimed cast iron, but the majority were still performing their original function.  The stone-work needed no re-pointing, the ox-blood and lime mortar having stood the test of time.

While crossing I had also noticed a feature that I had been vaguely aware of - the canal extends under the towpath.  There are a small number of grills that allow the water to be seen underneath.  I suspect many people don't notice, and some would be scared to look down in case the view is of the river below instead.

The advantage of this design is that there is somewhere for the water to go when a boat comes by.  A narrower trough would take much more effort to cross.  Only a handful of the cast-iron supports for the towpath needed to be replaced when it was serviced.

The visitor centre had pictures of the aqueduct being serviced, including the water being drained from a plug above the River Dee.  When full the trough contains 1800 tonnes of water.  The flow from the feeder delivers that much water every hour.

Next to the visitor centre there is a pair of dry docks.  These are similar to a lock with gates or planks at one end, but no exit at the other.  One of the docks has a building over the top of it and is still used. Its neighbour is open to the elements.  I was intrigued to see the plug on a chain at the far end.  Water was finding its way through the wall from the other dock and draining away.  It's always best to build a dry-dock where you have a good water supply, and somewhere to drain the water out.  Both of these are in abundance here.

The rain has continued for most of the day, so we have taken advantage of our secluded spot for a quiet, mostly indoors day.  We haven't even had many gongoozlers passing by.