If they are three-cornered, it is probable that the object glass is subjected to undue pressure in its cell.
Curiously the others crowded about the object glass of the periscope.
What the diameter of the object glass was we do not know, perhaps two inches or possibly a little more.
The apparatus for this purpose consists of three condensing lenses and an object glass.
The refractor achieves this by means of a carefully shaped lens, called the object glass, or objective.
No doubt if this had been the case, a perfect telescope could have been produced by properly shaping the object glass.
The power which I usually employ magnifies but one hundred and fifty diameters; and I use the entire aperture of my object glass.
The body of the instrument is entirely covered with thick brown paper, its length being 25ft., and the object glass 12in.
Each half of the object glass forms a separate image of any star at which the telescope may be pointed.
Each degree of my scale is equal, however, with the object glass employed, to .002 Mm.