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Zacharias Janssen is generally believed to be
the first investigator to invent the compound microscope. most scholars believe that his father, Hans, must have played an
important role in the creation of the instrument.
The device fashioned by the Janssen’s, and
described by Boreel, rose vertically from a brass tripod shaped like dolphins and was almost two and a half feet long.
Zacharias Janssen was a Dutch lens-maker who invented
the first compound microscope in 1595 (a compound microscope is one which has more than one lens). His microscope consisted
of two tubes that slid within one another, and had a lens at each end. The microscope was focused by sliding the tubes. The
lens in the eyepiece was bi-convex (bulging outwards on both sides), and the lens of the far end (the objective lens) was
plano-convex (flat on one side and bulging outwards on the other side). This advanced microscope had a 3 to 9 times power
of magnification. Zacharias Janssen's father Hans may have helped him build the microscope.
The microscope may have been invented by eyeglass
makers in Middelburg, in the Netherlands, invented sometime between 1590 and 1610. Hans
and his son Zacharias Janssen are mentioned in the letters of William Boreel (the Dutch envoy to the Court of France) as having
invented a 20X magnification microscope.
Robert Hooke used an early microscope to observe
slices of cork (bark from the oak tree) using a 30X power compound microscope. He published his observations in "Microgphia"
in 1665. In 1673, Antony van Leeuwenhoek discovered bacteria, free-living and parasitic microscopic protists, sperm cells,
blood cells, etc., using a 300X power single lens microscope.
The invention of the microscope is variously
accredited to Zacharias Janssen, a Dutch spectacle maker, c.1590, and to Galileo, who announced his invention in 1610. Others
are known for their discoveries made by the use of the instrument and for their new designs and improvements, among them G.
B. Amici, Nehemiah Grew, Robert Hooke, Antony van Leeuwenhoek, Marcello Malpighi, and Jan Swammerdam. The compound microscope
is widely used in bacteriology, biology, and medicine in the examination of such extremely minute objects as bacteria, other
unicellular organisms, and plant and animal cells and tissue—fine optical microscopes are capable of resolving objects
as small as 5000 Angstroms. It has been extremely important in the development of the biological sciences and of medicine.
The origin of the optical microscope is a matter of debate, but most scholars agree
that the invention of the compound microscope can be credited to Zacharias Janssen in the late sixteenth century. At that
time eyeglasses were beginning to enjoy widespread use and this focused a great deal of attention on optics and lenses. The
microscope illustrated above was built by Zacharias Janssen, probably with the help of his father Hans, in the year 1595.
Janssen's microscope consists of three draw tubes with lenses inserted into the ends of the flanking tubes. The eyepiece lens
was bi-convex and the objective lens was plano-convex, a very advanced compound design for this time period. Focusing of this
hand-held microscope was achieved by sliding the draw tube in or out while observing the sample. The Janssen microscope was
capable of magnifying images approximately three times when fully closed and up to ten times when extended to the maximum.
No early models of Janssen microscopes have survived, but there is a candidate housed in the Middleburg Museum
in Holland that some historians attribute to Janssen.Curiosity is the driving force behind any invention. It also could
have been what inspired a 16th century inventor to create a device that would allow people to learn much more about the world
in which they live. This device has helped people through the ages learn more about diseases, study the human body, discover
tiny factors in the world around them, and become aware of primitive organisms that also call the Earth their home. What is
this amazing invention? The compound microscope.