Bausch & Lomb Jug Handle Model CAH Microscope

[garyjm]

Greetings fellow enthusiasts!

Many years ago, I acquired this microscope, but I am only now getting around to wondering about its history.

I see F.H. Thomas Company on the plaque but I cannot find out anything about them. I do see a lot for Arthur H. Thomas Company. Were they related?

The serial number is 78613 which means it was made in 1909.

I see it has oblique illumination by moving the lower iris diaphragm via rack and pinion. I don't seem to find this feature on modern microscopes. Was this just in vogue during this time period?

What is oblique illumination used for?

All motions on this microscope work well. I will be lubricating the gears. I have no knowledge on how to restore the brass. It must have been a beautiful site when new.

I'm attaching a few photos.

Thanks!
Gary

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[apochronaut]

. Distributors of scientific equipment would cut deals with manufacturers and based on that the degree of exposure each would get would vary. There are Bausch & Lomb microscopes from the pre.W. W. I era out there that have only the distributor name on them. The Thomas companies, you may be able to research separately.

Your microscope has had at least one objective replaced sometime in the 1930's or 40's. There was no chrome plating prior to 1922.

The purpose of oblique illumination is/was to cast a shadow on the object being viewed. By manipulation of the degree of shadowing and diaphragm control, a large degree of detail in the sample could be made availalable to a good objective lens. It in some ways was a precursor to modern relief contrast systems and provided early bacteriologists and protozoologists with a great deal of information with which to base their detailed drawings on.

[garyjm]

Thanks Apochronaut for your reply.

I should have added that the plaque also shows Bausch & Lomb. Attached is a close up of this.

I wonder how much this microscope is worth? I'm not planning on selling but am just curious.

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[apochronaut]

There isn't a lot of intrinsic value to microscopes of that type and era yet, unlike brass ones from even 25 years earlier. There were a lot made. It also isn't in entirely original condition. The little brass seal is the insignia of the "triple alliance", a cooperation between Bausch & Lomb, Saegmüler and Carl Zeiss. Each company benefitted somewhat from the other's technology and was able to manufacture, distribute or utilize certain designs of the other two companies under license. That all ended with W.W.I.
It's value is more related to what it can do, which is pretty average optically but with the oblique, somewhat more capable. Jug handle types were favoured in situations where the microscope had to be moved a lot, such as in a university biology lab.
It was made in a time when B & L was still using a 1" eyepiece, so the field of view is somewhat larger than it's contemporaries. The oblique diaphragm is nice but based on catalogue information, mounted on an average 1.2 abbe condenser. It would have some value if it was on a 1.4 N.A. achromat aplanat condenser and with apochromat objectives. The objectives are achromats, so average. If it had a good remote microscope lamp it would still be a good average grade achromat microscope, with the added bonus of oblique illumination, something not available on modern microscopes. Imaging should be quite decent if properly set up.
If I owned it and was selling it , I would be very happy to get 150.00 for it but even 100.00 would be great. A case would help.

[garyjm]

Well, I'm just happy owning a piece of history. I will have to check my microscope collection and see if I have something older.

I'm fascinated with microscope history and the different companies and how they interacted with each other. Not to mention the great inventors.

It's greatly appreciated having experts like you that can speak about the vintage stuff