Contact lens and electrical telegraph: what they have in common

1. Step 1. Contact lens — evolved from — Glasses. A lens right on the eye.
2. Step 2. Glasses — evolved into — Telescope. The first telescopes were assembled by spectacle makers.
3. Step 3. Telescope — is used in — Optical telegraph. Signals were read through a telescope.
4. Step 4. Optical telegraph — evolved into — Electrical telegraph. The electrical telegraph replaced semaphore lines.

Open Evothings