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Archibald Williams explains the scientific principles behind common mechanisms and physical phenomena such as steam, electricity, light, and hydraulics. The text focuses on the fundamental operation of everyday devices rather than specific models or detailed technical specifications.

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Table of Contents

HOW IT WORKS.

colours:— Green , signifying distant signals; red , signifying home and starting signals; blue , signifying facing points; black , signifying trailing points; white , signifying spare levers. These different colours help the signalman to pick out the right levers easily.

To the front of each lever is attached a small brass tablet bearing certain numbers; one in large figures on the top, then a line, and other numbers in small figures beneath. The large

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