Cellulose and electrical telegraph: what they have in common

1. Step 1. Cellulose — is material for — Celluloid. Nitrocellulose.
2. Step 2. Celluloid — is material for — Sunglasses. The frames are celluloid.
3. Step 3. Sunglasses — evolved from — Glasses. Glasses with dark lenses.
4. Step 4. Glasses — evolved into — Telescope. The first telescopes were assembled by spectacle makers.
5. Step 5. Telescope — is used in — Optical telegraph. Signals were read through a telescope.
6. Step 6. Optical telegraph — evolved into — Electrical telegraph. The electrical telegraph replaced semaphore lines.

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