For additional images of diatoms from this slide please scroll down.
DESCRIPTION
This is an example of a type slide (in German, Typen-Platte). It is a one-hundred-form example mounted in styrene (refractive index about 1.55). It is in fantastic condition except for some bubbling of the mountant, but this does not extend into the field of the specimens which are nearly all exquisite. The condition of the diatoms and the quality of their mounting is evident in these images.
HISTORY
Edward Thum was one of the best, and perhaps the greatest of the diatom mounters. Originally an instrument maker, at age 28 he turned most of his attention to mounting, and formed the Institut fur Mikroscopie in Leipzig, Germany in the fourth quarter of the 19th century. He merged with another company about 1906 but continued to mount until his death in 1926. His specimens are beautifully mounted and valuable and included slides of individual species, beautiful arrangements and Typenplatte like the one featured on this page. He apparently also made a few special slides, such as monograms on request. He mounted both in Styrene and in Monobromonaphthalene, the latter with a higher refractive index about 1.66, which allows higher resolution, but perhaps less satisfactory for long-term preservation. Thum was also a trained machinist and sold Algunsuchers and other diatom-related equipment, probably of his own make. The slide featured on this page was listed for sale for $12 in 1895 which would be $462 in 2025. The great diatomist Henri van Heurck described the Algensuscher as Thum's invention and noted some of them had interchangeable doublets to allow magnifications varying from 60 to 100X; such an outfit sold by Leidig in Nuremberg and produced about 1915 is on this site.
