From John Quekett's A Practical Treatise on the Use of the Microscope, 1852 

M. Nachet's Microscope For Chemical Observations.

This very valuable instrument is represented in fig. 265, and is composed of a solid foot, X, in which is fixed the piece, O, for the reception of the small plate, P, on which the objects to be examined are placed; as in this instrument we view the under surface of objects, the illumination must be on their upper surface; for this purpose we fix at pleasure to the piece O the rod T, which holds the mirror, M, and the piece, D, for holding the diaphragms, polarizing aparatus, &c. To the foot, X, is attached a dovetailed slide, V, in which is contained a prism, R, supporting the tube, A, and the body, C. Supposing that a particular object is to be viewed, by means of the two milled heads, B, we draw the prism, R, out of the axis of the instrument, as shown in fig. 266, we screw the object-glass to the piece F, we replace the prism under the small plate, and then adjust the focus by means of the tube A and the fine adjustment, F. 

There are in G, fig. 266, two screws, which, coming in contact, prevent R from coming out completely. The office of the prism, R, is to receive the image in a vertical direction, and reflect it to the axis of the body, C, which carries the eye-pieces without any perceptible loss of light. When an object is required to be very much heated, a larger plate, the edges of which are heated by small spirit- lamps, is laid upon the small plate, P. The magnifying powers to be obtained in this microscope vary from 25 to 500 diameters, and all the apparatus necessary for the study of mineralogy can be applied to it, such as the goniometer, micrometer, &c. In short, in the general use of acids, reagents, &c., no injury can happen to the lenses of the object-glasses, as, being placed underneath, they are protected from the oxidizing vapours.

From The Microscope in its Application to Practical Medicine by Lionel Smith Beale, 1858

Microscope for Examining Substances immersed in Acids and corrosive Fluids.In examining preparations which require to be immersed in strong acid, in the ordinary microscope, it is not easy to prevent the fumes from injuring the brass work of the instrument. Considerable inconvenience is also experienced in examining fluids while hot, in consequence of the vapour which rises, condensing on the object- glass, and rendering the object invisible. These inconveniences are entirely obviated by the ingenious microscope invented some years ago by Dr. Lawrence Smith, of Louisville, United States. This was made by M. Nachet, of Paris, and has been described as Nachet's chemical microscope.*

The inverted chemical microscope is represented in fig. 106, in which also the form and position of the prism are shown. By this arrangement the object-glass is always kept perfectly clear, while of course the definition of object is not in any way interfered with. In order to adapt the instrument to drawing the outline of objects with the glass reflector, 76, it would only be necessary to have the body fixed at a right angle with the axis of the object-glass. A small mirror at an angle of 45 degrees, might be substituted for the prism

* In the first edition of this work I must regret having inadvertently omitted Dr. Smith's name as the inventor of this instrument. To him ls certainly due the merit of its invention. Dr. Smith's paper on the subject, will be found in the " American Journal of Science," second series, Vol. xiv., 1852.

The description of the microscope from the 1886 Nachet catalog:

This can be translated as follows:

38. - Inverted microscope for chemical studies
(fig. 26). - In this instrument, the objectives are placed below the object, one has not to fear that the evaporations prevent clear vision due to accumulation of vapours. - The stage is gilded. This microscope, with 3 objectives No. 3, 5 and 6, 1 eyepiece, and Goniometer for measuring the angles of crystals. Accessories: alcohol lamp mounted on an articulated base, object glasses, cover slips. In a mahogany box. . . . . . . . . . . 350 fr.   (I thank Jeroen Meeusen for this translation)