Photo by Naturenet
Here’s a wonderful idea by Joseph Cornell, author of Sharing Nature With Children:
If you listen carefully with a stethoscope, you can hear the “heartbeat” of a tree. Find a thin-barked tree more than 6 inches in diameter and place your stethoscope against its trunk. Be very quiet. Move the stethoscope around until you can hear the crackling, gurgling sound of sap flowing up to the branches.