A Cause of Damage to Optical Glass in the Tropics

Deterioration of the glass of microscope objectives, telescope lenses, prisms and expensive optical glass of all kinds has always been a source of worry to those using optical apparatus in the tropics. Many theories have been advanced to explain this damage, but as far as is known few, if any, of these have ever been definitely proved. In the present investigation, one cause of the clouding of prisms has been definitely established, and a remedy has been suggested. The work is not complete and further research on the lines indicated below will probably produce fresh facts, but it is felt that the matter is of such importance that these notes should be published even in their present state of incompleteness. Certain prisms were submitted to the writer with a request for an explanation for the clouding of their polished surfaces, which recurred