William Beaty wrote:
> How microscopes REALLY work (Leeuonhouk's great
> secret, & wrong texts)
I'm not sure what you mean by that. I hate to put myself forward as perhaps a
leading expert on this subject, but from what I have read, I have probably the
most practical experience with what Leeuwenhoek actually did rather than what
people think he did. His microscopes were prized by everyone who could get a
hold of them, because as tiny single lenses they produced a far sharper image
than the compound microscopes of the day. This was simply due to the fact the
the chromatic and spherical aberrations were so exaggerated by the compound
microscopes that they produced a much inferior image. Contemporaries were
astounded at the quality of the tiny lenses.
Of late, the assumption has been made that Leeuwenhoek simply drew out a glass
fiber in a flame and then fed it back in to create a spherical droplet which
was then mounted in its holder. The types of flint glass available at that time
were unlikely to produce the marvelous clear images of Leeuwenhoek's
instruments on account of refractive index striations and bubble inclusions.
One other problem is that no one seems to have noticed is that many, if not
most of Leeuwenhoek's microscopes were plano-convex lenses, not spheres.
As a child, I made many microscopes like Leeuwenhoek's. I learned quickly that
ordinary flint glass gave poor results. Borosilicate glass (Pyrex) gave much
better results, but Leeuwenhoek didn't have that as far as I know. After
making the spheres, I would embed them in Burgundy pitch and then grind and
polish a flat side. This can be done very quickly on such a small piece.
These were just wonderful little lenses, but it nagged at me that the Dutch
lensmaker didn't have Pyrex. He might have had a special glass formula that
gave equivalent results, but knowing what I do of the glasses available from
that era, I don't know what it would be.
But it is possible that Leeuwenhoek had access to borax. I discovered that if
you melt borax on a polished metal surface, you get a bunch of little glass
blobs, most of which are irregular shapes or have bubbles. But a significant
number of the molten droplets are nicely symmetrical plano-convex lenses with
excessive curvature at the edges. The over curved parts can just be blocked
off with an aperture having a smaller diameter than the lens. Voila! Instant
no effort microscope. Did our Dutch hero do it this way? There are so few of
the hundreds of beautiful little microscopes he made that it would be a shame
to do any destructive testing on one. So I guess we'll never know for sure. I
doubt if anyone but me is interested enough to find out anyway.
Hey, I'll bet that's more than you guys ever wanted to know on this subject.
M.
