Before radios and reliable tide tables, and when the depth of silt in the harbour may vary – all those factors made entering a harbour a risk. Thus an indication of the state of the tide and the depth of water in the harbour was indicated by a ball raised or lowered on a mast. Workington harbour had a similar arrangement.
A red ball by day or a red light by night shown from the Watch Tower at Lonsdale Dock denotes a depth in the harbour of 8 feet or more. Two red balls or two red lights denotes that navigation is impeded. From 8 feet flood to 8 feet ebb a red light is shown from the wood pier and a green light from North jetty. The channel to Workington is marked by white and green lights. Two red leading lights show deepest water in entrance.
Changes in the depths in the inner waters of the Firth of Solway are very rapid, and the chart should be used with caution.