Nachet Inverted Microscope for Chemistry Studies (No. 366)

This is a rare example of an inverted microscope for chemistry studies made by the Nachet company from c1855-1910. The chemistry microscope of this style was invented in 1850 by J. Lawrence Smith, Professor of Chemistry at the University of Louisiana, and was manufactured commercially a few years later. Nachet catalogs describe it as an “Inverted microscope for chemistry studies”, and sold it for 350-375 fr. This particular instrument is probably of a later manufacture date, perhaps c1892. A thorough description of the microscope and its use was published by J. Queckett soon after its introduction (1855). The microscope was designed to be used for analysis of substances immersed in corrosive liquids, or chemicals that needed substantial heating to be investigated. An inverted configuration was critical for these applications, as conventional upright microscopes would be damaged by the heat and corrosive fumes.

The microscope is set on a very heavy and stable circular base. Set in a dovetail slider is the objective and microscope tube assembly, inside of which is a prism for transmitting the image from the objective up through the eyepiece tube to the observer. The dovetail allows the objective assembly to be slid out and away from the stage so the objective can be exchanged. This instrument comes with only one, low-magnification objective. On the back of the base is the support mount for the circular stage and the shaft that supports a circular holder for a polarizer or other accessory, and the mirror assembly. The microscope comes with two eyepieces, No. 1 and another unmarked, as well as a goniometer assembly that contains a calcite crystal. This accessory would allow the operator to measure birefringence angles of sample crystals.

Focus is via two mechanisms. Coarse focus is accomplished by sliding the objective collar up or down; the position of which is held by friction. Fine focus is accomplished using a thumbscrew on the right side of the instrument that moves the objective assembly via a fulcrum device.

The microscope comes with a large, black metal sample heating stage insert. It has a circular locating collar that fits into the stage cutout, and four offsetting legs that raise the heating insert several mm above the brass sample stage. When in place the heating insert overlaps the stage. This allows it to be heated by an external flame. The microscope comes with a mahogany carrying case.