Thread by @James_Taite

There’s an old story I just made up about a mason, spending his days piling stone on top of stone. Raising a church.

He’s asked by the abbot: “We build for the glory of God; how do you intend to keep the stones standing through years of wind and frost?”

A thread…

“Simple, I put something heavier on top, to keep it in place”, the stonemason replies.
“And how do you keep that from falling?”
“Well I put something even heavier on top.”
“And on top of that?”
“Something even heavier…”

Something heavy all the way up.

Stonemasonry is a celebration of mass. It depends on its weight for stability. This is the principle behind those tall pinnacles that top buttresses. The logic behind that inert burden of material filling the haunches of vaults and arches, keeping them from spreading and failing.

It’s no accident that copers tend to be larger than the walling they sit on. In a sound wall, individual stones are kept in place by the weight of the stone above. And at the top of the wall, kept in place by their own weight. Walls need big stones on top. The heavier, the better

Which makes stonemasonry the art of lifting heavy things high.

One of the most common methods of lifting stone is the use of slings. Choke a rope or nylon strap around the load. Simple, straightforward, and safe, requiring little specialized knowledge or gear.

But another group of lifting devices displays an elegance—a daring—absent in boring old slings. They rely on the weight of the stone itself to secure it for lifting.

That’s ingenuity: when you have something heavy to lift, devise a plan that depends on the thing being heavy.

The pic above, and the first image at the top of this thread, show the use of dogs, a pair of teeth that grip opposite sides of the stone. Dogs can be either in the form of scissor-like tongs or separate implements connected by a chain passing through a ring on each tooth.

In either case, when the stone is lifted the dogs are pulled together horizontally, gripping it. The heavier the stone, the harder the dogs bite.

By their weight they rise.

Dog-holes are easy to make. But when the dogs are in the ends, stones can’t be simply butted together in the wall; and when the dogs are used front and back, they leave visible divots. No problem in a workaday structure like the walls of this lock, but otherwise undesirable.

The 2-pin lewis employs the same principle as that of the dogs, but the point of purchase is moved from the sides of the stone to its top bed. 2 holes are drilled at an angle; the pins grip like fingers in a bowling ball. Stones can now be landed side by side in the wall.

As with dogs, a chain or cable or strap passes through rings on the end of the pair of pins. And as with dogs, the horizontal pull of the chain against the pins causes them to bite in the holes.

The split-pin lewis is composed of 2 semi-circular halves that combine to make a single leg, fitting in a single round hole drilled vertically into the top bed: less work to prepare than the 2-pin lewis. The two arms of the split-pin are connected by links to a larger ring.

When lifted, the bent arms lever against the sides of the hole, producing friction between steel and stone. This friction, and only this friction, holds the stone in the air.

So that hole’s gotta be clean of dust. Real clean. NO, REALLY CLEAN.

This particular split-pin is rated for a safe working load of 3 tons; seems crazy, but the friction generated here will lift more than 6000 lbs. And it has been used to raise stones almost that heavy: the cornice of the temporary home of the Senate of Canada for example.

By their weight they rise: all these devices rely on the mass of the stone. Despite their capacity to lift enormous loads, there is a delicacy—a risk—to their use. A jerk or jump or bump might momentarily remove that load, causing the bite to fail and the stone to fall.

So it’s vital that the fixer mason be gentle when manoeuvring those 1000s of lbs of stone and resist the impulse to push or pull on the lewis, or ‘help’ by lifting an end.

And health & safety officers really really really don’t like them, often limit their use to short lifts.

The exception to this principle is the 3-leg lewis: a trio of vertical steel bars, the middle bar with parallel sides and the outer 2 tapered from bottom to top; the whole resembling a dovetail. A shackle straddles the 3 legs and all are drilled in line to take a bolt.

The seating for the 3-leg is a rectangular mortise, undercut (or wider at bottom than top) to match its profile. This takes time and care to cut; it must be the full depth of the lewis and fit tightly, shaped so that contact is at the bottom of the mortise.

The 2 outer legs are dropped into this hole and the centre leg inserted between them, pushing the outer legs apart and into contact with the sides of the seat, preventing them from slipping out. The shackle is placed over the ends of the legs and the pin slid through.

The 3-leg relies on its assembled shape for security. It is unique among lewises because it keys with the stone, locked in place by the bolt.

And another name for the 3-leg is ‘St. Peter’s Keys’, maybe referring to its appearance, maybe to the surety of its form.

Keys had long been a symbol of Saint Peter and the papacy, taken from the text of Matthew 16:18-19.

“[Y]ou are Peter, and on this rock I will build My church[…] And I will give you the keys of the kingdom of heaven”.

Just a pun on Peter and petrus (Latin for rock) conflating material foundations with moral support.

But introducing the 3-leg lewis complicates the metaphor, comparing the act of building to worship, and the authority of the master builder to that of the bishop of Rome…

…Crossed wires and conflations; like that Christian mechanism of salvation by the sacrifice of Christ, that Ascension realised by taking up the burden of the cross and the world’s sins. That weight by which transcendence was effected...

Something heavy all the way up.

Illustration credits in the alt text.