MODEL RELEASED. Seismometer experiment. Two pupils with a makeshift seismometer, a device used to measure seismic waves in the Earth's crust. These waves are often caused by shifts in the Earth's tectonic plates. The pencil on the spring responds to vibrations, drawing representations of them on the paper. In order to pick up such minute tremors a seismometer needs to be enclosed, to protect it from movements in the air. To cut out local vibrations it also needs to be fixed onto a large immovable surface, such as a block of stone. Since this apparatus is on a table in the open, it is wholly ineffective.