For three years, students at a hillside school have kept a record of the weather from a small station on the roof of the science building. The equipment is modest. A rain gauge collects water in a narrow tube, and a thermometer sits inside a ventilated white box that shields it from direct sunlight. Every morning at eight o'clock, two volunteers climb the stairs to read both instruments and enter the measurements in a shared notebook.
At first, the readings seemed unremarkable. Warm days followed cool ones, and storms arrived without much warning. Over time, however, the students noticed something curious. Their rain totals were consistently lower than the figures published by the airport across the valley, even after storms that had soaked both places equally.
Their teacher encouraged them to investigate rather than assume the airport was mistaken. The students examined the gauge and discovered that an air vent nearby was blowing across the opening of the tube. On windy days, some of the falling rain was pushed aside before it could be collected. The difference was small for a single storm, but it accumulated over months.
The class moved the gauge to the opposite corner of the roof, away from the vent, and compared the two locations for several weeks. The new position matched the airport far more closely. In their report, the students explained that an instrument is only as reliable as the place where it is installed. They also added a note to the old records, so that anyone reading them later would understand why the early totals were too low.