Lens Story: 4 of 28
application of glass to spectacles. The eminent
American optician, Mr. John A. Brashear, places the date of this discovery
as being "somewhere between 1280 and 1311." Preserved in an Italian
library is a manuscript written in 1299 in which occurs this sentence:
"I find myself so pressed by age that I can neither read nor write
without those glasses they call 'spectacles,' but lately invented."
OPTICAL SYSTEM OF NEWTON'S|
To whom belongs the credit for first having
used lenses in some form of optical instrument has never been settled.
As early as 1590 a Dutch optician,
Zacharias Jensen, placed convex
and concave lenses at the ends of a tube about eighteen inches long and used
the combination for the purpose of magnifying small objects.
OPTICAL SYSTEM OF GREGORY'S
A fellow countryman,
a few years later experimented with a similar arrangement of lenses and
made the discovery that a distant church steeple was brought much nearer
by their aid. But to the genius of Galileo
Galilei, Italian musician, scholar, teacher, physicist, inventor and
astronomer, the world will forever be indebted for the invention of the
astronomical telescope, an instrument that has extended the bounds of
human observation by millions of miles.
Galileo's telescope, or "Optical Tube," as he
called it, consisted of a lead tube in one end of which was a double
convex object glass, and, in the other, a double concave eyeglass.
OPTICAL SYSTEM OF
With this first instrument he brought objects three times nearer
and made them appear nine times larger. He quickly made other glasses,
each of higher power than the preceding, and, in a short time, had a
telescope that brought objects thirty times nearer than when viewed
with the naked eye. With this instrument Galileo made his epoch-making
discoveries in astronomy. To his amazement he found that he could count
OPTICAL SYSTEM OF
as many stars as his unaided eye was able to detect. Contrary
to the common belief, then, the stars were not all equidistant from
the earth. Those that were brought into view with his telescope, he
concluded, must be at greater distances than those seen without its aid.
He next turned his magic tube on the
SYSTEM OF LENSES IN