This material is admirably adapted to the purpose because it gives
way certainly, though very slowly, to the pressure of the glass.
In order that it may have room to change its form, grooves are cut
through it in both directions, so as to leave it in the form of
squares, like those on a chess-board.
[Illustration with caption: THE OPTICIAN'S TOOL.]
It is then sprinkled over with rouge, moistened with water, and
gently warmed. The roughly ground lens is then placed upon it, and
moved from side to side. The direction of the motion is slightly
changed with every stroke, so that after a dozen or so of strokes
the lines of motion will lie in every direction on the tool. This
change of direction is most readily and easily effected by the
operator slowly walking around as he polishes, at the same time
the lens is to be slowly turned around either in the opposite
direction or more rapidly yet in the same direction, so that the
strokes of the polisher shall cross the lens in all directions.
This double motion insures every part of the lens coming into
contact with every part of the polisher, and moving over it in
every direction.
Then whatever parts either of the lens or of the polisher may be
too high to form a spherical surface will be gradually worn down,
thus securing the perfect sphericity of both.
Pages:
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127