The experimental physicist
We know that from the time he returned from his educational tour Klingenstierna often introduced physics, optics, and mechanics into his lectures. His remarks about the translated book Inledning til Naturkunnigheten (Introduction to Understanding Nature) (1747) revealed his fascination with experimentation, for instance when he describes various experiments with people holding charged glass bottles and giving off sparks. The book concludes with some advice to the reader:
”One must take pains to carry out these trials with the greatest assiduousness and make note of any further remarkable phenomena that might occur.”
When he became our first professor of experimental physics in 1750 he himself had new opportunities to find those further remarkable phenomena.
Klingenstierna had seen to it that the University purchased the most modern equipment for his experiments. In 1738 he spent 6,000 daler in copper coins on a considerable collection of instruments from England. The collection included e.g. a vacuum pump, an electricity machine, a Laterna Magica (a projector of sorts), and a microscope.
The interplay between physics and mathematics that we see in Klingenstierna also bore fruit in another connection. In both his Principia (1687) and his Opticks (1704) Newton had expressed doubt as to whether it was possible to construct a combination of lenses that would eliminate the diffusion of color that occurs in a lens owing to the diffraction of light. Klingenstierna demonstrated mathematically in 1754 how an achromatic optical instrument could be constructed. For this discovery he was awarded a prestigious prize from the Academy of Science in St. Petersburg in 1762.