Challenger Expedition

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 at http://www.19thcenturyscience.org/.

Thank you for any ideas,

Alan

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