Row of vertical access shafts and optical telegraph: what they have in common

1. Step 1. Row of vertical access shafts — is part of — Qanat. A chain of shafts for digging and ventilation.
2. Step 2. Qanat — is made of — Clay. Weak sections of a qanat were reinforced with clay rings.
3. Step 3. Clay — is material for — Oil lamp. Later — clay ones.
4. Step 4. Oil lamp — is used in — Magic lantern. The light source is an oil lamp.
5. Step 5. Magic lantern — has part — Lens. Lenses.
6. Step 6. Lens — is used in — Optical telegraph. Signals were read through telescopes.

Open Evothings