Last Friday we reached a peak in our canal-boating adventure, literally, because once you go through a lock called Mediterranee a few kilometres before Toulouse you are on the watershed of the Canal du Midi. This is the part of the canal where the water is introduced, originating from the Black Mountains to the north. Because canals aren't natural waterways, water has to be delivered to them and they constantly need to be topped-up. Eau really? Yes.

I'm not sure how, in the 1600s, Paul-Pierre Riquet and other engineer-types could accurately measure the height of a landscape, other than perhaps watching which way streams and rivers flowed, but they did a damn fine job. (Mind you, so too did the Romans 2000 years ago, constructing aquaducts that dropped just a few metres over hundreds of miles)

Anyway, having identified the Black Mountains as the best (and highest) source of water for the ambitious canal project, Riquet went ahead and solved all the problems of how to get the water from there to where it was needed - a canal that would join the Atlantic to the Med. This included building a preliminary feeder canal, storage dams and a dividing pound... ambitious projects in themselves.

So we feel slightly special having cruised to the point where it all began. Since starting on the Canal du Midi from the east, every lock we've encountered has taken us 'uphill', raising us a few metres at a time to a higher level. From tomorrow though we will be cruising downhill, since we have reached the peak of the Midi. Yes folks, from here on it's all downhill, at least to Bordeaux.

After our scare at the Bram lock where the boat threw itself into full reverse, we are being extra vigilant in our daily mechanical checks. Apart from the usual coolant level, oil level, coolant reservoir and battery observations, we now include a check of the throttle/gear mechanism, which is still operating on its makeshift repair. So far, so good, though after the Bram Incident I am still a bit nervous using the throttle in the confines of a lock. On Friday though we were blissfully on our own and didn't have to share any of the locks with other boats.

Watching the water cascade into the locks on this watershed day we felt quite humbled, firstly that the VNF - Voies Navigables de France (the French Waterways Network) - supply lock-keepers to operate many of the the gates and paddles that control the water flow, and secondly that these hundreds - if not thousands - of litres of water were being supplied and drained just for us.

Not that we get it for free; in order to travel the VNF-controlled waterways you have to buy a 'vignette' - a licence sticker that you put in your boat's window which declares what length of cruising period you've paid for, just like the tax disc or registration sticker on a car. We've optimistically opted for the whole of 2014, partly because we don't know how long we'll be sailing for and partly because it's cheaper the longer period you sign up for.

But despite nervousness in the locks the day passed without any major incident, and as we cruised towards the absolute peak of the canal I joked to Liz that we were approaching a 'Moses Moment', where we would witness the parting of the waters. Well blow me down if, when we got there, there wasn't a sign that said exactly that... 'Partage des Eaux' - 'Parting of the Waters'. And we looked upon the sign and saw that it was good. And we gave thanks. And the people fell to their knees and wondered, wherefor cometh such presience?

Dunno. Just a hunch.

So from there on the water level dropped. The supreme irony of the day - and perhaps God getting his revenge for my blasphemy - was that the boat's console alarm sounded and a little warning light lit up. It said, 'Check Water Level'. For some reason it indicated it had started to go down.

Spooky.