Firearm and hydraulic press: what they have in common

1. Step 1. Firearm — uses — Gunpowder. Powder gases.
2. Step 2. Gunpowder — evolved into — Dynamite. A replacement for gunpowder in mining.
3. Step 3. Dynamite — works like — Tunnelling shield. Two ways of driving tunnels — mechanical and explosive.
4. Step 4. Tunnelling shield — uses — Hydraulic cylinder. The shield was pushed forward by jacks.
5. Step 5. Hydraulic cylinder — is part of — Hydraulic press. Two cylinders of different diameters.

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