The Board of Trustees of the Science Museum
Chinese incense clock.
How did we know what time it was before clocks? We had to be creative. Here’s how the incense clocks of medieval China and Japan worked.
Today, telling the time is an even more automatic gesture than it was a few years ago, when we still had to raise our wrist and, some faster than others, “translate” the hands. Now, we always have our cell phone in our hand, always ready to tell us if we’re going to arrive on time. However, for much of human history, measuring time required some creativity.
Before mechanical clocks, and long before atomic clocks, humans turned to shadows, water, candles, and even scents.
Os sundialsbased on the shadow projected by a gnomon, were for a long time a simple solution to keep track of the passing of the hours. However, they had a major limitation: they did not work at night, nor on very cloudy days. To overcome this problem, several civilizations have developed alternatives.
In Ancient Egypt, for example, they were already used water clocks at least since 1350 BC, according to . They were devices that measured time through the controlled flow of water from a container. Marks inside indicated the passage of time, although it was necessary to compensate for the reduction in water pressure as the level fell. Initially, these mechanisms were mainly used to measure short intervals, similar to an hourglass.
Ctesíbio’s water clock, developed in the Alexandrian period, was used both by doctors to measure pulses and in courts to limit the length of speeches. But these devices continued to require visual observation.
The incense clocks
In medieval China and Japan, incense clocksalso known as fragrance watches.
In China, these mechanisms would have appeared before 520 AD and were based on the controlled combustion of aromatic materials.
The simplest versions worked similarly to marked candles: burned at a predictable rate, allowing the elapsed time to be calculated. Others were more elaborate, using trails of powdered incense divided into equal segments. As the combustion progressed, the user could follow the passing of the hours.
Some of these watches went even further. Certain markers placed along the trail could be made from different aromatic mixtures. When the fire reached each point, it released a specific smell, allowing the time to be identified by the aroma.
In other versions, small balls fell when the incense burned to a certain point, thus signaling the change of time by sound.
Although today they survive mainly as historical curiosities or decorative objects, these clocks show the extent to which the measurement of time was, for centuries, a matter of sensory imagination.
Before we looked at the time, there were those who could smell it. And, as ZAP already recalled, there were those who sold them:
