Moseley's Microscope

Moseley stated he used a Hartnack's Number 4 objective and No. 4 eyepiece. Here's a picture of a Hartnack with a Number 3 (10X) eyepiece.

I received the following response on the sci.techniques.microscopy group to my inquiry:

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".