September 7th is Van Leeuwenhoek day. Everyone is encouraged to sample some local freshwater aquatic microscopic life and to show the wonders of this fascinating world to others perhaps unfamiliar with it. This annual event was suggested by a fellow amateur microscopist Wim van Egmond (Netherlands) who lives close to the freshwater lake where Van Leeuwenhoek sampled and who made the first report of aquatic microscopic organisms in a letter dated Sept. 7th 1674 to the Royal Society. Wim and fellow microscopists will be sampling at the location where the lake once was. Microscopes available for use will include Foldscopes.
Wim has prepared an illustrated pdf article summarising the historical background to this suggested annual event, link Avl-day.pdf. An old map is overlain with a Google Maps aerial image to show where it all started. For folk who have the single lens paper Foldscope it would be especially appropriate to use it and show the capabilities of a single lens. It was high power single lens microscopes that Van Leeuwenhoek developed to a high degree and with which he first reported the existence of aquatic microorganisms.
The first such organisms accurately described and recognisable in the letter was a cyanobacteria Dolichospermum. Wim came to this conclusion after careful studies of the original letter text in Dutch and his local knowledge of the lake sampled. This assignment to Dolichospermum is becoming widely accepted instead of the earlier assignment to the algae Spirogyra. An example of where an amateur microscopist like Wim can make useful contributions to microscopy.
The image shows the current location of where Berkelse Meer once stood.