British steamships were powered by the miners of South Wales and the North of England. Without coal, there was no steam.
If you were the master of a British steamship, responsible for safely conveying passengers and your crew from, say, London to Auckland NZ, you would not wish to run out of coal mid-voyage, and there was little risk that you would. At the start of the BT27 passenger list period in 1890, it was probably not untrue to say that Britannia still ruled the waves and the Government controlled a network of strategically-placed coaling stations ocean-wide for the use and benefit of the mercantile marine as well as the Royal Navy.
There were 14 main coaling stations in British possessions, at which vessels could refuel. Spinning your globe anti-clockwise from the international date line, the 14 were King George Sound and Thursday Island in Australia; Hong Kong and Singapore in the Far-East; Trincomalee and Colombo in Ceylon; Mauritius in the Indian Ocean and Aden at the mouth of the Red Sea; Simon’s Bay and Table Bay in South Africa; Sierra Leone in West Africa and St Helena in the South Atlantic; and, finally, Jamaica and Castries Bay, St Lucia in the Caribbean. There were of course smaller coaling stations, such as Esquimalt in British Columbia and Perim in the Red Sea. Steamships were of course amply provided with coal, as well as other necessaries such as food and water, before they left British shores for their destinations worldwide, but the existence of coaling stations ensured that ships weren’t caught short and that passengers reached their destinations without inconvenience.