While searching the index of "The Practical Astronomer" an 1850 book by Thomas Dick marked Vol. IX, I came across an article about Dr. Barlows experiments with fluid lenses and his success in constructing very high quality astronomical telescopes. Dr. Peter Barlow was the inventor of the Barlow Lens, used widely in optical instruments. The short article has a wealth of information on what materials he used and his designs, along with observations he made to test the optical properties of the instruments. A preserved piece of astronomical history that took place over 160 years ago.
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Clear Sky - Rich