To make stones, which are by definition quite heavy - mostly rocks that have irregular shapes and sizes, and are decidedly hard to shape; to get them to stick together for any length of time in a normal dry stone wall, is quite an accomplishment in itself.
To get them to stick together for any length of space, over thin air without support from below, seems like a different thing altogether.
The proper name for it is corbeling. It's a kind of counterbalancing - getting stones to overhang each other gradually without tumbling over. I guess there will always seem to be a bit of magic to it . And yes maybe there are tricks to making it work, but those who study this sort of thing will say it's merely physics. Which kind of takes the element of risk away yes, but some of the fun and wonder too, I think.
Closing over our temple, by stepping over the space contained inside our 8 foot high circular wall, having a 16 foot diameter, using tons of only random shaped rocks, does sound a little adventurous!
That's because it is.
Our dome starts slowly
The first few circular courses of stones creep imperceptibly towards the center pole. None of the courses of stone hang over more than a half inch . As more courses are added the extent of 'creeping over' increases slightly .
At first it seems like the sides of the dome are only going up! This is disconcerting. The higher we go the more intensely we say to ourselves "shouldn't it start stepping into the middle a lot more?"
But such is the shape of a dome - or half sphere. It seems to not change much until nearing half way up the arc. And all the time it's just getting higher and higher, and why would anyone want to build a dome any higher than absolutely necessary? But the fact is , to make a smooth semi spherical arc the overhang needs to be barely noticeable until higher up.
And it's then, higher up, that the radius string-line and the curved template form are indicating that you need to slide (dangle?) the stones further over and deeper into, and over, the abyss. This is where things start to really get exciting. Never mind physics. This seems just foolhardy .
But no. The physics and the adrenaline tell us to go on. Mindful of the risk, but drunk on the excitement of building such a cool structure, and with physics on our side, not worrying about the hangover, we continue stacking stones, not actually on top of each other, but slightly off-to-the-side-of-on-top-of each other...stepping 'up and over', and 'over and over', further...
To be continued
