Mike Tuke’s

Making a pebbleometer A pebbleometer is used to measure the diameters of pebbles. It is easier to use than callipers and unlike metal callipers does not rust, this is important if measuring which may be wet especially by the sea.   Requirements Strip of wood 38cm x 5cm x 2cm 2 blocks of wood 6cm by 6cm by 5cm 1 piece of plywood 5cm by 6cm 1 opaque 30cm ruler 2  4cm, 2  2cm and 3 1cm brass screws Instructions for making 1  Screw and glue one block onto the end of the strip of wood. 2  Glue and screw the plywood onto the second block so that it over laps it by 1cm. 3  Varnish all the wood 4  Carefully saw off the part of the ruler below 0cm. 5   Drill 3 countersunk holes into the ruler and screw the ruler to the strip with the zero end tight against the fixed block. Instructions for use Place the pebble on the ruler and against the fixed block. Place the second block on the ruler with the flange against the side of the strip.  Move the second block so that it touches the pebble. Remove the pebble and read the measurement on the ruler at the edge of the block.

Earth Science Activities and Demonstrations