Book 30, Question 47
How can you measure a lake's temperature at different depths?
Tie a thermometer to a string with a small weight and lower it from a dock or shore, with a grown-up.
Wait a minute, pull it up, and read it quickly. Record the temperature at the surface, one meter down, and further down. Draw a graph with depth on one side and temperature on the other. In summer you will see a drop in the thermocline.