so
in the late 1700s canal mania had gripped britain and it was been a fascinating era to be around in
engineers of their time trying to grapple with the long philosophized problems of the
era notwithstanding high infant mortality rate lack of medicine and of course pretty
horrendous living conditions but all that aside never before had man attempted to traverse the
landscape in such a bold way the desire to move heavy goods such as coal across the land
without using rutted trackways was was very much topic of the day and of course the desire to to
move up and down the land on water without wasting that water itself was very much on the agenda
and so to south west england where one of the biggest issues of the day
was getting from bristol to the south coast without going all the way around land's end
and cornwall of course the dangerous
peninsula
you join us on the grand western canal and we're in search of a curious canal invention that
had the potential to change the way canals traverse the landscape forever so with the
grand western canal having this huge ambition and excuse the graphic here with that they built
the first nine mile section really quickly the tiverton to loudswell was done in four years
albeit with no locks lifts or inclines required that was complete by 1814
so the tiverton to loudswell section was complete at the 90 meter contour
that's important to remember because the next section was getting down to taunton
at a 15 meter contour level and that was obviously such a big problem it took another 15 years
for them to even get started on that so much so they employed a local engineer called john green
he'd worked on the Bude canal he'd worked under John Rennie so he knew what he was doing he even
built an incline on that beard canal so he knew how to deal with gradients but for this canal that
was obviously a bigger task a bigger undertaking so he proposed another incline and seven of these
so these were boat lifts which used a philosophical principle from half a century
ago by somebody called anderson not to be confused with anderton we'll come back to that principle
shortly and the way in which james green employed it on the canal but despite this there were issues
and from 1830 progress on this section of the canal was very slow to the point in 1836 james
green was actually dismissed it would take another four years for this canal to fully open thereafter
in 1838 two years after his dismissal james green
wrote all about these these lifts and how they worked and all their intricacies
and it gave the people of today the archaeologists of today a real insight into how they worked and
the problems they encountered along the way that was 1838 but they carried on building the canal
despite what is just to my left here which is the bristol nxt railway opened in 1841
so this is nine head lift and it's one of the only surviving ones today
it's been dug out it's been excavated and then studied in many different ways now it's not a
new principle james green even in 1830s admitted that oh well there you go there's a train look
james green even admitted it wasn't a new principle he wrote about the anderson principle
he acknowledged we think he acknowledged uh fossils over in the dorset in somerset
which used a similar principle so the idea being in this section here would be the canal the boat
would go in and just at the end where the the arches are they would go into a cast on
now the castles were held in two separate tubs and they'd have a large wheel above them
which would balance them the idea being if you had water in one water in the other it wouldn't
take a great deal to just move them slightly and move them up and down it's a very very
obvious principle but there are a lot of teething problems with it which we'll come to very shortly
so here we are at the very windy end of the nine head aqueduct and following on
for the nine head lift just over there now there was one mistake that james green made
now based on the anderson principle it meant that one of the castles had to have a slightly
less amount of water in it even a couple of inches and that meant that when the other side went down
it would sink low enough the boat could leave the castle just by simply opening the lock below
he didn't do that and he always had the same amount of water in each and it led
with all sorts of technical problems so much so that on three of those lifts including this
one here he had to build another lock just the other side of it so if you look on the other end
of this lock here or this uh lift here you'll see some additional locks and that to my mind
almost defeats the object of having one of these beautiful lifts here in place
so let's take a look at the design of one of these lifts on the ground western canal designed
by james green here is a side on profile view the large wheels at the top with chains holding
the cast-ons which would in turn hold the boats inside them you jack each cast on against each end
and you would open the guillotine type gates to keep them watertight and off you'd venture down
to the next section of the canal so let's put our caissons on the location of this picture where
they would have been raised and lowered and flip this to a view from above this is the design that
james green thought would work on seven different locations helping to get the boats down to taunton
and more importantly save a lot of water as the boats made that journey a massive advantage over
the more traditional locks but because of this imbalance that we talked about because he kept the
water level the same unlike anderson has suggested the locks had to be installed on at least three of
these lifts to help with that journey down them so there it is in all its glory the beautiful uh
james green nine head lift and of course the uh based on the principle of the anderson lock but
with a slight change hence the need for a couple of other locks in front of it which probably
defeated the object of the whole lift in the first place perhaps if it wasn't for the iron
road behind it coming in 1841 here they brushed to an extra perhaps if it wasn't for the design flaws
from james green this canal would have become more of a prominent feature of western england
so the wind and the rain has come in now but why not because it's the start of june so
that completely makes sense for a british summertime crazy canal invention that james green
tried to uh undertake a beautiful architecture
it's beautiful structure that's still there today but perhaps the worst thing was the execution