Here's a classic and elegant nineteenth century experiment that's still popular in an age of electronic and computer measurements. The apparatus consists of a glass tube 90cm long. One end of the tube is closed with a stopper and the other end is open. An aluminum rod, with a disk on one end slightly smaller than the diameter, is inserted into the open end. By moving the rod and disk, students can vary the effective length of the vibrating column of gas in the tube. You set the rod into vibration at its natural frequency by stroking it with a piece of rosined leather to create a high pitched note. The dust or powder inside the tube will collect into heaps at the nodes. The wavelength of the standing waves is then determined from the separation of the dust heaps. From this you can calculate the speed of sound. Includes instructions. Requires a piece of leather. Overall length is 112cm