October 19, 2010 #090 - Barlow's Fluid Lenses

Over the years I have seen a few references to lens constructed of liquids. For instance opticians and experimenters have tried various methods of using "quick-silver" or mercury to form concave mirrors to be used in reflecting telescopes. I've even seen references to the use of ice, in attempts to produce suitable mirrors and lenses. Everything I have read about has major drawbacks.

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.

(Click on picture to enlarge for reading)

Clear Sky - Rich