Brewer's: Watch on Board Ship

There are two sorts of watch- the long watch of four hours, and the dog watch of two, from 4 to 6; but strictly speaking a watch means four hours. The dog watches are introduced to prevent one party always keeping watch at the same time. (See Wolf, Between dog and wolf, Dog-Watch.)

There are two divisions which perform duty alternately- the starboard watch and the port watch. The former is called the captain's watch in the merchant service, often under the command of the second mate; the port watch is under the command of the first mate.

The Black Watch.

The gallant 42nd, linked with the 73rd, now called the Royal Highlanders. The 42nd was the first corps raised for the royal service in the Highlands. Their tartan (1729) consisted of dark blue and dark green, and was called black from the contrast which their dark cartans furnished to the scarlet and white of the other regiments.

Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894

Watchet

Watch Night