Society, Politics & Law
Seismograph
...open mouth of the frog directly below it. By finding out which frogs contained balls after a strong earthquake, Zhang Heng could work out how the earth had moved in response to the earthquake. How to make a seismograph What you’ll need: A base to put it all onto (wood is easy to use) A pole to hang the pen and weight from A rod that hangs from the pole and is free to...