Ship canals climb hills using locks — chambers that fill and drain, walking a vessel up the terrain one step at a time. The Panama Canal lifts ships 26 m over three stages. But what about a serious climb? The Continental Divide is 3,400 m in Colorado. Even a modest transalpine link would need a kilometer of vertical relief. A staircase of locks won't work — you'd drain a river. So build a ship elevator: a caisson of water hoisted vertically like a skyscraper's freight lift.

Existing ship lifts prove the concept: the Falkirk Wheel (Scotland) rotates 24 m using 22.5 kWh per swap; the Three Gorges lift (China) hoists 3,000-tonne barges 113 m in 40 minutes. We're proposing to multiply that by nine.

The physics gift: Archimedes. A ship displaces its own weight in water, so a caisson holds the same mass whether the ship is aboard or not. Counterweight the caisson and the theoretical lifting energy is zero — you're only fighting friction, cable stretch, and wind.

Sizing a caisson for Panamax-class vessels: 300 m long × 35 m beam × 4 m deep of water = 42,000 m³ ≈ 42,000 tonnes. Balanced against an equal counterweight, only friction losses matter. Estimate 5% mechanical inefficiency:

E_loss = 0.05 × m × g × h
       = 0.05 × 4.2×10⁷ kg × 9.81 × 1000 m
       ≈ 2.1×10¹⁰ J ≈ 5.7 MWh per lift

That's a bargain — about $600 of grid electricity to move a container ship one vertical kilometer.

Now the structural nightmare. The caisson hangs from cables loaded to 42,000 t. High-strength steel wire rope tops out around 1,960 MPa working stress. Required cross-section:

A = (4.2×10⁸ N × safety factor 4) / 1.96×10⁹ Pa
  ≈ 0.86 m² of steel — a bundle 1 m in diameter

Feasible, but a 1,000 m cable of that gauge massses 6,800 tonnes on its own — 16% of the payload. Elastic stretch under load: ΔL = FL/AE ≈ 2.5 m. The caisson will bob at the top like a fishing lure until you add hydraulic dampers.

Wind loading is the killer. A caisson presenting 300 × 15 m of side area (1,500 m²) at 1,000 m elevation sees gusts of 40 m/s routinely. Drag force ≈ ½ρv²C_dA = 0.5 × 1.2 × 1600 × 1.2 × 1500 ≈ 1,700 kN — enough to swing a Panamax like a piñata. You'd need a guided track (roller bogies riding a concrete spine), effectively a maglev shaft the size of the CN Tower.

Water accounting justifies it. A traditional lock staircase 1,000 m tall (40 Panama stages) burns ~8 million m³ of freshwater per transit — a small reservoir per ship. The elevator uses the same 42,000 m³ every cycle, recirculated. In a mountain-pass canal, water is scarcer than steel.

Verdict: buildable at ~$15 billion (extrapolating from Three Gorges' $6B for 113 m). Worth it only where a canal already exists on both sides — say, connecting two watersheds through a single Andean pass. Otherwise, the ships can just take the long way around a continent, because they're ships.