Re: Challenger Expedition

Well, you are in a bit of luck...

A relative of mine was a botanist from right about that time period
and my Grandmother gave me his microscope a number of years ago. It's
a beautiful instrument (and happens to be the same microscope being
asked about here), so I do fully understand the sadness of the loss of
such a microscope as here expressed...

Anyway, to get to the point, in this microscope I have the "Table of
Magnifying Powers" as originally written by this distant relative of
mine... With my microscope, there are two eyepieces labled 2 and 4 and
there are two objectives labeled 4 and 7. The other point of interest
in this microscope, is that there are two positions of the tube that
holds the eyepieces, an "in" position and an "out" position. This
changes the tube length, hence changing the magnification as someone
has pointed out already in this discussion...

Here is the table of magnifying powers:

Eyepiece 2, objective 4: in 45X out 85X
Eyepiece 2, objective 7: in 125X out 225X
Eyepiece 4, objective 4: in 100X out 170X
Eyepiece 4, objective 7: in 255X out 450X

dj

On Aug 8, 1:24 pm, UKOncol...@xxxxxxx wrote:
On 7 Aug, 22:06, Alan <lngn...@xxxxxxxxx> wrote:





On Aug 8, 4:56 am, pennin...@xxxxxxxxxxx wrote:

On Aug 7, 4:07 pm, Alan <lngn...@xxxxxxxxx> wrote:> I have been reviewing earlier work on Millepora spp. Moseley, aboard
the Challenger, 1873-1876, mentioned study of Millepora sp. through
Harnack's objective No. 4, eyepiece No. 4. I wonder whether anyone
on this list would have a clue of the meaning of this, or where I can
find out.

Also, any particulars on the microscopes used aboard that vessel? I
found mention that Microscopes were carried aboard. I thought I'd ask
some of the experts here before digging deeper into the literature,
that is so laborious to download athttp://www.19thcenturyscience.org/.

Thank you for any ideas,

Alan

Hi

Not a historian but recently borrowed the splendid book by van Heurck
'The microscope' English translation by W E Baxter 1892 to form the
5th edition according to Preface.

There is a table of Hartnack's objectives on page 167 ...

The No 4 objective is listed as 'Equivalent focus ' 10 mm and
'Numerical Aperture' 0.5.
The mag of this would depend on what tube length microscope it was
used on. ca. 16x on a 160 mm

If it's the same no. 4 objective as the one the above author refers
to, he remarks on it on page 165: Quote:

"No. 4 is an excellent objective. It is very clear, and its powers of
definition and penetration are very remarkable."

If the Hartnack's eyepiece conforms to an earlier note in this book on
eyepieces but might not, p71: Quote:

"Thus the ocular 4 amplifies the image given by the objective four
times".

regards

David

Thank you. I have found the fNo. 3 eyepiece is convertible between
10X and 3X. I wonder whether the No. 4 is also convertible? All of
this information is useful.

Alan

I used to have a Hartnack until some *** burglar stole it. My dad
bought it for me, and it was my first real microscope, built in Paris
around 1860. Although unsophisticated by modern standards, it was
beautifully engineered and the quality of the optics was excellent,
even by modern standards. I can't remember the numbers on the
objectives, but one was low power - about x5, and the other was about
x40, comprised of three stacked unscrewable lens elements so that
intermediate magnifications could be achieved. I still mourn the loss
of this instrument after 30 years, and every detail of it is in my
memory - one day I'll find it......so watch out for me Mr Burglar...- Hide quoted text -

- Show quoted text -


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