Volume Thirteen - Pre-Victorian to the Present Day - Remarkable Connections - Darwin, FitzRoy, Hawkshaw & Wedgwood . . . .

FitzRoy and the Weather - A New Science for the Mariner

For the sailing vessels approaching Penarth Dock and the Ely Tidal Harbour, the weather was not simply a matter of comfort. It could determine whether a ship reached harbour safely. The entrance to the Penarth Dock was near the mouth of the River Ely, facing the Severn Sea. The approach to the Tidal Harbour combined a narrow and demanding entrance with powerful river and tidal movements, exposed waters and the hazards of a coastline containing rocks, mud-banks, shoals and changing conditions.

The site of Penarth Dock itself had one important advantage ; it was closer to deep water than the Bute Docks at Cardiff and was sheltered from heavy seas and high winds by Penarth Head, but once a vessel was outside that shelter, the Severn Sea, Bristol Channel and Atlantic Ocean presented a formidable and unpredictable environment.

The extraordinary Bristol Channel tide - The Bristol Channel and Severn Estuary are renowned for their exceptional tidal range. The Severn Estuary has been described in scientific literature as having the second-highest tidal range in the world. The funnel-shaped Bristol Channel contributes to this extraordinary rise and fall of the water level especially near Penarth. Fundamentally, seawater from the Atlantic Ocean is forced by tidal forces dependant upon the relationship of the moon and sun to the earth. Contributary factors include wind and wave actions which drive the seawaters up the ever decreasing width and depth of the Bristol Channel i.e. the volume of water remains almost the same but the cross-sectional area decreases hence the level of water and speed increases.

At spring tides, tidal currents may exceed 1.5 metres per second over extensive areas and for considerable periods. Storm surges, strong winds and powerful waves could add another layer of danger. For a nineteenth-century sailing master, this meant that wind and tide had to be considered together. A favourable wind could be cancelled by an adverse tide. A vessel waiting for sufficient depth could find the weather deteriorating and a sudden gale could turn a manageable passage into a dangerous one remarkably quickly.

This was the environment in which FitzRoy's new meteorological system became particularly significant.