We recently saw the projector based on the Duboscq arc lamp. Today's video introduces a nifty optical attachment: a microscope. Intense light from the projector passes through a slide containing a prepared specimen. A system of lenses focuses a magnified image of the specimen upon a screen.
Using a microscope is ordinarily a solitary activity. Only one person sees what's on the slide. This device allows a teacher and students, in a darkened room, to examine specimens together. Not only is this valuable in teaching about the specimens on the slides, but it can also be helpful in training students how to see when they later use conventional microscopes.
In 1665, during the early days of microscopes, the English scientist Robert Hooke prepared an elaborate book of drawings, Micrographia, that would introduce readers to the newly-visible world of the very small. The showpiece of the book was Hooke's masterful drawing of a flea.
In the centuries since, in textbooks, Hooke's famous flea has often introduced students to microscopy. So it seems fitting that in Florence, the slide we see projected is a flea. It's traditional!
The Foundation for Science and Technics, or Fondazione Scienza e Tecnica, of Florence, Italy, has made available many videos exploring the Cabinet of Physics, a large collection of antique scientific demonstration instruments. The Foundation's homepage may be found here, and its Youtube channel, florencefst, here.