How to make a candle clock?
Moving forward on our time telling timeline, today, we came to the 9th century AD, and the English king, Alfred the Great's, nifty invention of the candle clock (which really should be called the candle alarm clock, or candle timer). Although, King Alfred was credited with this clock, according to Encyclopedia Britannica, similar devices were also being used in China during the Sung dynasty (960-1279), though they used incense, which would be pretty cool, because you could change scents throughout the day.
We used two identical, except for the color, birthday candles, to make a scaled down version of the clock.
Then we lit one of the candles, marking it's height every minute on the candle next to it. If you decide to try this at home, be careful, not to burn your finger in the process.
We discovered the birthday candles burned 1/2 centimeter per minute. On a bigger candle, you could write the amount of time passed, between each mark.
King Alfred used the candles to divide his days into periods of study, prayer, rest, and so on. Of course, he couldn't have had a fruitful rest, or prayer time, if he'd had to watch a candle out of the corner of his eye - but that's where the ingeniousness of this clock comes in. If the candle was placed over a metal plate, and a tack was stuck into the candle at the appropriate time, then as the candle burned down, and the wax melted, the tack would fall onto the plate, and alert the King, that time was up.
We had to try this out for ourselves, too. So, we put a tack in our marked candle, at the five minute mark. We set our oven timer for five minutes, lit the candle, and busied ourselves making lunch.
When we heard the tack hit our plate, we glanced at the oven timer, where there were two seconds left. We didn't think a two second error was bad, and it had worked just like clockwork!