Being able to know the time at any given moment is a modern convenience, or perhaps an annoyance. Not so long ago, people would pay to learn the correct time, and even further back in human history, we’d approximate the time by the shadows a gnomon cast on a sundial.
Mechanical clocks, atomic clocks, and shadows aren’t the only ways humans have tried to keep track of the hours and minutes. In fact, we came up with quite a few new ways to do it, mostly because sundials don’t work very well, as expected, in the middle of the night or cloudy weather.
In ancient Egypt, water clocks were used as early as 1350 BC. They measured time by allowing water to flow out of a container at a known rate, and markings within the container would indicate the current time.
It sounds simple, but ancient people had to figure out ways to account for the slowing of the water flow because of falling pressure, which made this timekeeping device quite handy. Nevertheless, these water clocks were mostly used for monitoring short intervals of time, bearing more resemblance to an hourglass than a true clock.
Over time, more sophisticated water clocks were developed, including the water clock of Ctesibius, which was accurate enough and used for a variety of purposes.
“During the First Alexandrian period, the clepsydra of Ctesibius was adapted to take a patient’s pulse by physicians,” explains Lisa Knox in the book “Robot: A History of the Robot.” “They were also used in courts for timing speeches. A long tube was submerged in water, and when it filled, the opening at the top was capped. When it was reopened, water dribbled out of a small hole at the bottom end. A person could speak until the tube was empty.”
While these were good clocks, you still had to look at them to tell the time, which, as we all know, is a real hassle. In medieval China and Japan, inventors developed clocks that solved this problem in the form of “incense” or “fragrant” clocks. These appeared in China even before water clocks, around 520 AD.
The simplest of the “burning clocks,” not to detract from the underlying idea, were candles that burned at a known rate, with markings on their sides to indicate how many hours had passed since they were lit. This form was the most common of the “burning clocks,” but not the most sophisticated.
“Additionally, there was the ‘incense seal,’ which was a continuous trail of powdered incense, marked off at intervals so that an observer could measure the passage of time with relative accuracy as the incense burned,” explains Silvio A. Bedini.
But these clocks still required peeking, which, as already mentioned, is unbearable. As a significant advancement, clocks were developed that would burn until they reached certain markers along their path, at which point they would begin to emit their own distinct smell. In some versions of the clocks, you could also tell how much time had passed since they were lit by looking at which chimney the smoke was coming out of.
“It is quite possible that pegs or plaques with zodiacal symbols inserted along the incense trail to mark the time intervals may actually have been plaques of solid incense, each made up to a different recipe,” adds Bedini. “When the gradual burning of the trail reached one of the markers, that marker, too, would burn, and the priest attending the service could tell by the smell how much time had gone by.”
In short, one could tell the time by smell. Some of them had an additional system with balls that would fall when the incense burned out, allowing you to hear the change in time as the balls clattered into a tray below. Unfortunately, these clocks are no longer in use, except as curiosities.
About the Author
