There is something magical about an arch. It is a joy to consider. Any well built arch naturally causes our eyes to follow the line of carefully fitted stones, as they define the weightless open curve of space that their heavy mass defies. The arch of a stone bridge, the interior vault of a magnificent church or the arched entrance way to a garden, are all applications that inspire us because of the inherent loveliness of their simple shape holding up such an enormous amount of weight. It seems almost like an illusion or some clever allusion to the realm of metaphysics.
Actually an arch is a straight forward visualization of pure mechanical physics. Expressed in simplest terms the arch shape is unique because it converts tensile stresses of the structural members into compressive stresses only. Stone is weak in bending strength and cannot span significant distances without collapsing under its own weight. By configuring it into an arch, the force of gravity is redirecte
And that was the case of the arched garden feature we built recently at Canada Blooms, inside the Convention Centre in Toronto 2005. Many thousands of people came and marvelled at the structure we built during that show. Our humble arch constructed of random shaped granite, was something we did basically to demonstrate that you can build with stone structurally, without glue or cement. We call it our "party piece", basically drawing people's attention to the concept that you can build walls here in Canada just like the ones you see all over the UK. We were surprised that this dry stone arch wowed the visitors as much as it did. People were amazed that it stood there without anything holding it up . They were also very cautious about walking under it.
For the five days of the show, tens of thousands of people arrived at Blooms by walking along the enclosed Skywalk that connects Union Station to the Metro Convention Centre. Union Station is an incredible feat of architectural engineering. It stands as a monument to Roman ingenuity and modern technology. There are arches and vaults of stone in the main ticket lobby nearly 88 feet high! It is an inspiring thing to look at these stone arches gracefully suspended in air by the force of their own enormous weight. I sat there in the station and marvelled, as I ate my Egg McMuffin one morning, before I began the long hike over the Skywalk to the South Building. What keeps those stones up?
That people were more amazed by the small arch we built at Blooms and never even considered the huge arches they had already walked under to get there, seemed a bit ironic. I pointed out to several people that it wasn't the cement that was holding up the huge stone vaults of Union Station. The stones in those massive arches stayed in place essentially for exactly the same reason they did in our tiny arch. I described it as "pushy stones all trying to get down through the same narrow opening at the same time". If people were going to cower as they walked under our arch, they had better be wary walking back through Union Station too.
I was pleased to consider the impression that our lovely little dry stone arch had made on everybody. Evidently in the case of this arch, small is not only beautiful, it is somehow more amazing!