Rubber

This afternoon we bought William a new bike. It is bigger than his old one, it's got 20 inch wheels and a five speed gear system built into the handlebar. He's a bit unsteady getting started on it but is really starting to be able to go. The larger wheels allow him to ride on grass and gravel better.
Speaking of rubber, but not rubber, June 15 is the 140th anniversary of the unsuccessful entry into a competition to replace the ivory in billiard balls. The inventors in question, John and Isaiah Hyatt, patented the "solid collodion" evolved into celluloid, the material that became the base for flexible film and thus an essential ingredient in motion pictures.