Word: flintglass
(lookup in dictionary)
(lookup stats)
Dates: during 1880-1889
Sort By: most recent first
(reverse)
There has been invented a new form of telescope object glass which can be transformed at will from a "photographic" to a "visual" lens by simply turning over the crown-glass lens and changing its distance from the flintglass lens. The Clarks have made for Professor Pickering a lens of this construction with an aperture of thirteen inches and a focal length of fifteen feet...
| 1 |