Lens Story: 12 of 28
PART OF SOLAR SPECTRUM
The manufacture of camera lenses has become
a highly specialized art, as rigidly exact and painstaking as the
making of a large refractor. So large must be the output of these
lenses that much of the hand grinding and polishing has long since been
superseded by the motor-driven machine. And yet the skilled artisan is
as indispensable as ever. The grinding is carried to an accuracy of one
fifty-thousandth of an inch. Then, after a most critical inspection,
each lens is centered in a lathe and mounted.
If it may be said that the telescope has brought
to our knowledge new worlds without end, so is it equally true that
the microscope, penetrating the universe in the opposite direction, has
revealed systems of life and matter as truly marvelous as the infinite
depths of space.
Until 1870 the compound microscope was a very
imperfect instrument. Up to that time it had been built on the same
general plan as the telescope. Its defects were fully appreciated, but
no one knew how to remedy them.
Then Professor Abbe of Jena,
the master genius of modern optics, attacked the problem and successfully
solved it. He corrected every aberration and designed an objective
which is today the basis of all compound microscopes. In this objective
are six lenses, the smallest of which is only one-sixteenth of an inch
in diameter. The machinery for grinding it is a marvel in itself, and
the grinding is done by trained technicians who have worked at the art
from boyhood. They can tell by touch the progress of the work, and the
finished product must be as perfect as the largest refractor.
As the name signifies, a compound microscope gives
double magnification. The objective itself frequently gives a primary
magnification of 95 diameters, which is multiplied by the eyepiece to
This is about the limit for practical work, although
magnifications of 3,000 diameters are possible.
Coupled with the camera and the arclight,
the microscope gives the microphotograph. The value of the microscope
to science can hardly be estimated. Biology, bacteriology, the causes
of disease, a knowledge of the structure of metals and crystals, have all
been made possible through its marvelous powers of penetration. The wave
length of light, itself, has imposed a limit to these powers, and further
magnification is impossible. But just as this crisis arrived the
SETTING DISKS IN GRINDING SHELL