Coal is both bulky and very messy stuff. Early steam ships – that’s until the arrival of what’s known as the triple-expansion steam engine in the 1880s – were chronically inefficient consumers of it to boot. Up until the 1860s, a typical 700hp engine would have needed up to 50 tonnes of coal a day.

Hong Kong’s Harbour Master’s statistics are pretty useless and there is no hard data on steamship numbers before 1873. In that year 1579 steamers entered the port. Data suggests ships loaded around 100 tons of coal on average when they called at Hong Kong, so we’re looking at an annual demand for bunker coal in 1873 of around 150,000 tons.

The average ship delivering coal from the 1840s until the 1870s was a sailing ship and only carried about 400 tons, so we’re looking at anything up to one ship a day having to arrive in Hong Kong to ensure there was enough coal to meet the demand. To begin with coal was mostly a cargo of opportunity. Because, for colonial Hong Kong’s first forty or so years, demand in China for British products was very weak, ships leaving from Britain carried coal as ballast so the voyage could earn some money. Later, they carried British goods to Australia, picked up a cargo of coal there for Hong Kong, and then loaded tea to take back to Britain.

Only certain organizations with predictable demand – like the P&O steamship company or the Royal Navy – had regular, dedicated deliveries. For the rest, it was down to the market to ensure that supply matched demand. Mind you, however it was shipped for whatever reason, coal was a tricky cargo. There are lots of stories of coal carrying ships catching fire (in certain conditions coal will spontaneously combust) and exploding or sinking. There are others of the cargo shifting in strong weather and ships capsizing – a few ships are reported setting out from Britain with coal for Hong Kong and never arriving, just disappearing somewhere en route.