# Building a Simple Water Clock IELTS Academic Reading - 13 questions - 20 minutes - Diagram labelling, Flow-chart completion, Summary completion (word list), Short-answer questions Source: Written by Testmigo. ## The passage You should spend about 20 minutes on Questions 28-40, which are based on the passage below. Long before mechanical clocks, people measured time by letting water flow from one container into another. The earliest known water clocks, from Egypt and Babylon, were simple stone bowls with a hole near the base. As water escaped, the falling level inside the bowl showed how much time had passed, although the flow slowed as the bowl emptied, which made the hours uneven. Later designers solved this problem by keeping the water at a constant height. In the version described here, water is poured into an upper container called the reservoir. An overflow pipe near its top carries away any extra water, so the depth in the reservoir never changes and the water leaves through the outlet at a steady rate. The water drips through a narrow brass nozzle into a tall cylinder below. Resting on the surface inside the cylinder is a float, usually made of cork or light wood. A thin rod rises from the float, and its pointer moves upwards against a marked scale as the cylinder fills, one division for each hour. Building the clock takes some care. First, the reservoir is filled and the overflow is checked. Next, the nozzle is adjusted until exactly one litre of water passes through it in an hour, which is measured against a reliable timepiece. Finally, the scale is marked by recording the height of the pointer at the end of each hour over a full day. Water clocks were valued because they worked at night and on cloudy days, when sundials were useless. Their main weakness was temperature: cold water flows more slowly, so a clock calibrated in summer could lose almost twenty minutes a day in winter. Some builders in China placed their clocks indoors near a stove to reduce this error. ## Questions ### Questions 28-30: Diagram labelling Label the diagram below. Choose ONE WORD ONLY from the passage for each answer. 28. The upper container 29. The part the water drips through 30. The object resting on the water in the cylinder ### Questions 31-33: Flow-chart completion Complete the flow-chart below. Choose NO MORE THAN TWO WORDS from the passage for each answer. Fill the reservoir and check the **(31)** _____. Adjust the nozzle so that one **(32)** _____ passes through in an hour. Mark the scale by recording the height of the **(33)** _____ each hour for a full day. ### Questions 34-37: Summary completion (word list) Complete the summary using the list of words, A-H, below. - **A** night - **B** uneven - **C** temperature - **D** stove - **E** metal - **F** steady - **G** summer - **H** sunlight Early water clocks measured **(34)** _____ hours because the flow slowed as the bowl emptied. Later clocks kept water at a constant height so it left at a **(35)** _____ rate. Unlike sundials, water clocks worked at **(36)** _____, but changes in **(37)** _____ affected their accuracy. ### Questions 38-40: Short-answer questions Answer the questions below. Choose NO MORE THAN TWO WORDS AND/OR A NUMBER from the passage for each answer. 38. What were the earliest known water clocks made from? 39. How much time could a summer-calibrated clock lose per day in winter? 40. What did some builders in China place their clocks near? [Practice online with a timer and instant marking](https://testmigo.com/ielts/reading/building-a-simple-water-clock) - [Answers and explanations](https://testmigo.com/ielts/reading/building-a-simple-water-clock/answers)