Raspail’s microscope

Do you ever regret something you’ve written? Every so often, I write something so inane in this column that later my toes just curl. In last month’s column, devoted to Ernst Ruska’s development of the electron microscope, I made an off-hand remark about how little optical microscopes penetrate into the lives of most chemists. It was only after I’d signed off on the text that I began to realise the silliness of my dismissal. Sure, atoms and molecules, even nanoparticles, are too small to see optically. But microscopes have nevertheless played a central role in the development of chemistry.

The demand for optical equipment after Antonie van Leeuwenhoek’s first reports of microscopic ‘animalcules’ resulted in rapid advances in lens technology and in the improvement of the microscope itself. In the winter of 1738–39, the German doctor Nathaniel Lieberkühn presented a couple of microscope designs at meetings of the Royal Society in London. The instrument maker John Cuff, whose workshop was just a few doors away, saw these demonstrations and decided that he could do better. In his design the single lens was mounted on an arm that also held a circular stage onto which samples could be placed. Below this was a circular mirror that could be tilted to reflect light onto the stage itself. The lens could be moved in three dimensions, allowing microorganisms to followed as they swam along.