Zentmayer "Grand American" Microscope
The Grand American was Joseph Zentmayer's largest and most deluxe stand, built from 1858 to 1876, when it was replaced with the American Centennial stand. During this period, it was considered America's finest microscope. This is No. 652 and is marked in script "J. Zentmayer, maker, Philadelphia".
The drawtube is calibated in 1/10" to 4". With fully extended rack and drawtube, the instrument is 25" high. Minimum height is 18". The objective is unsigned and relatively low powered. Zentmayer had a habit of not signing his optics, likely not anticipating the extreme interest in his instruments in the 21st century. The lack of the great variety of mineralogical accessories suggests this instrument was used primarily for biological specimens. It appears that these elaborate instruments were purchased primarily by well-to-do amateurs. Physicians could buy microscopes to suit their needs for under $100 from most of the American makers, while the Grand American cost over $700. An exception might be minerology professors, who could better utilize all of the movements and available accessories.
This instrument is inscribed on the main tube "A Testimonial to Rev. P.B. Haughwout by his friends". Haughwout was a Baptist preacher in Jamestown, NY, in 1869, and, in Ridgeway, Orleans County, NY, in the 1855 census. P.B. Haughwout was also a preacher in Fall River, Mass during the civil war. I'm not sure if these were the same person or which one had the honor of looking at God's work in a very expensive microscope.
The microscope is in fine working order, including the mechanical stage, fine and coarse focus, and optics. It is uncleaned, but has never met the wheel of the brass polisher. The finish is good, but not as good as most of the flash photos suggest. The silvering is mostly gone from the many silvered scales. A locking screw is missing from one of the two sliding brackets on the circular slide holder. The walnut case is also in fine condition.
closeup of substage parts. The large 2 sided mirror is mounted on a swinging tailpiece.
The nose mounted fine focus lever operated by a screw with graduated silvered knob. Also note the distinctive triangular opening in the limb, unique to the Grand American.
The mechanical stage is operated on the x axis via a worm gear and on the y axis via a fusee chain. Scales at the rear of the stage mark the movement on both the x and y axis. The rotating slide holder has a graduated degree scale on its chamfered edge.
The stand inclined 90 degrees for measuring angular aperture. The heavy base is well balanced for this purpose. This stand would be ideal for reenacting the "aperture wars" of the mid-19th century.
The mechanical stage scales.
The degree scale on the edge of the rotating slide holder
The achromat condenser with wheel of shaped stops. The top element of the condenser slips off to change the focal length. A separate wheel of round stops is also present and can be fitted on either end of the substage tube.
The stage mechanism.The left and right outer knobs turn the x axis screw. The inside knob on the left pulls the fusee chain y axis movement.
The large bullseye is original and stores in the fitted microscope box.
The walnut box is 19" high and in fine condition. The accessory box is not present and the only accessory is the bullseye.
small tight dovetails on the box. The brass handle and the lock and key are original and functioning.
The large mirror is in very good condition.Flat side
Concave side of mirror.Good silvering on both sides not shown in flash photos.
the substage - rear view.
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