The canal age really began in the 1700s, with the growth of cities requiring supplies of raw materials from greater and greater distances, overwhelming the primitive roads and horse drawn carriages available.
Barges had been used for centuries on natural waterways: slowly the realisation dawned that the rivers could be improved to maintain a constant level of water sufficient for navigation by adding locks and bypass weirs.
The deceptively simple invention of the angled lock gate and the development of waterproof mortar allowed the rivers to become arteries of supply. The lower cost per ton-mile of moving goods by water compared with the congestion-charged turnpike roads (sound familiar?) meant that it was but a short step to imagine joining the rivers together with artificial waterways.
The new science of surveying allowed canals to follow the contours of the ground where possible to minimise earthworks, and armies of navvies (short for "Navigators") dug the relatively shallow (often only 3 foot deep) channels and lined then with clay to make them watertight.

The results were the first superhighways, carrying goods, gossip and people between communities at a lower cost per ton than any other means of transport.

Construction of the canals allowed such engineers as Thomas Telford to exploit the compressive strengths of stone and the tensile strengths of the new cast iron to create aqueducts finally bettering the 2,000 year old Roman structures dotting Europe and the near East.The canal age lasted until well into the age of steam, before the finances of moving goods by the relatively fast railway finally did for all but some small scale coal movements.

In the 1960s, with the invention of the low-maintenance fibreglass pleasureboat and the development of reliable, cost-effective marine diesels, canals began a long, slow return to our hearts.
The money began to flow once more in to Canal Trusts and the British Waterways Board, and finally during the 1990s big deals with the Telecomms companies to lay fibre-optics along canal towpaths sealed BWB's finances to a sufficient extent that it could contemplate not only large-scale maintenance and the re-opening of long-defunct links such as the Blisworth Tunnel but the possibility of new canal construction such as the Bedford and Milton Keynes Waterway Trust project linking the River Great Ouse at Bedford and the Grand Union Canal at Milton Keynes, due to be completed by 2010 (unsurprisingly the bulk of the cost has been getting the ruddy Planning Permission!).

Even the Wendover Arm of the Grand Union Canal, abandoned in 1904 is being rebuilt and rewatered to provide leisure boating facilities to Wendover and Aston Clinton. This project has actually ben going for a number of years, is hugely professionally run and has even caused a major trunk road scheme to be modified to accommodate it. Well, I'm impressed....

We lived near the Aylesbury Arm of the Grand Union for several years and walked, in stages, the Grand Union from Kings Langley to Milton Keynes.

Canal towpaths are endlessly fascinating, as they move gently from rural to urban, from farmland to industrial scenery.
Around each corner is always a surprise: from fishermen to boats, from sudden strange military looking blockhouses to coxed eights.
The wildlife is abundant, and the intrusions of the modern world only tend to occur at bridges where the sudden appearance of cars seems other-worldly.

The appearance of the canal water can vary enormously: sometimes dirty brown and muddy, sometimes green and cloudy, sometimes smelly, sometimes clear and pure.

Unlike rivers, where the flow is always in one direction, as you walk a canal the flow is sometimes non-existent, sometimes in one direction (if you are walking vaguely uphill) then as you pass the summit or bottom the flow changes direction.

The other surprise, especially on the Grand Union, is the number of working boats. There are actually boats carrying coal, and the smell of burning coal on the wintery air brings memories for me of blustery days in Northern towns in the post-industrial-apocalypse early 1980s. It really is colder up North, I found when scouting for Universities and driving to Scotland for holidays.
They look pretty much like old boats you see in black and white films of the 1920s but have a lot more modern conveniences.