The convergence system of the two optical tubes is by means of the classic tube elevation mechanism to adapt to the interocular distance. Its macro focus system is by means of two wheels that act on the rear edge of the rack of the triangular support shaft. Fine focus is achieved by turning a horizontal wheel at the rear of the optical tube. The revolver is for two objectives and its condenser is by means of a diaphragm wheel. Its stand is in the shape of a «Y» or eagle’s claw (clawfoot), a foot frequently used by Charles Baker.

This model appears in their 1861 catalogue. The C. Baker Co. for the manufacture of scientific instruments was established in 244 High Holborn as early as 1769 and was in operation until 1959. It would be Charles Baker (1820-1894) who gave it its period of maximum prestige. After his death, several generations of descendants would still follow him.

The two optical tubes can be adjusted by means of a screw by varying the interocular distance. The coarse approach is carried out by means of two wheels that act on an endless screw; the micrometric consists of a small horizontal wheel located in its front part. It has a revolver with two simple objectives. Its plate is rectangular and moves in all directions thanks to a complex and precise system. It has three types of capacitors: a simple one with a wheel with nine openings, and also two composite optical capacitors. In order to obtain incident light, it has a large eight-cm “bull’s-eye” magnifying glass. in diameter and with a foot 30 cm high. This device is one of the first to have a three-point foot, a circular rear, the iconic “Crouch foot” or “English foot”.

Its large cherry wood case measures 44x24x22 cm. It contains seven objectives and three eyepieces, has three circular slides (live box) for the observation of small insects and three tweezers for handling samples. The microscope is 47cm high and its foot is 20cm wide and 15cm deep. On the back it bears the manufacturer’s name and its manufacturing number 1.003. Henry Crouch manufactured 10,145 microscopes. This Premier model was included in his catalog published in 1877 in the American Journal of Microscopy. It is also referenced in the Billing’s Catalog, 2nd edition on page 141, fig.264.

It has a mahogany case measuring 27 x 14 x 10 cm. Inside there is a small box for the five objectives, which are screwed on one after the other. This microscope was very deteriorated and its layer of varnish blackened; We have eliminated it by electrolysis, the apparatus having recovered its original shine.

Camille Sebastien Nachet (1799 – 1881) was a Parisian optician of the early 19th century. He started in 1834 making optical instruments with Charles Chevalier. Later he became independent in 1840 and established a small workshop on «Rue Serpente 16, Paris.» The first microscopes he made were based on the drum or barrel type models, like this one we present in the image. Nachet stood out for his contribution in adapting the adjustable binoculars to the microscope. Together with Chevalier and Oberhauser they are known as the top three microscope manufacturers of their day. He was succeeded in the company by his son Jean Alfred (1831-1908).

Under the platen and protruding from the rear is a wheel diaphragm with five openings. It includes two eyepieces as accessories and as objectives it has seven small lenses that screw on successively. It is stored in a 28 x 15 x 10 cm mahogany case.

This microscope was very deteriorated and its layer of varnish blackened; We have eliminated it by electrolysis, the apparatus having recovered its original shine.

The founder of the company was Noel-Jean Lerebours (1789 – 1840), an optician of great fame manufacturing high precision lenses for various firms. He made other models, but in small quantities, and designed a curious portable microscope: the «d´Amphiteatre» model, which is number 52f in this collection, a very rare microscope.

Its coarse focusing is done by a “reverse focus” mechanism by lifting the stage by a rack engraved on the back of the support shaft. Fine focusing is achieved by means of a horizontal wheel located on the axis of the apparatus. The illumination system for the metal sample that is placed on the stage is by incident light. It is generated by electrical system or acetylene light. It enters the apparatus through the horizontal tube that is placed over the objective. A magnifying glass with an articulated arm concentrates the light beam through a polarization prism, located over the central hole of the tube. These two pieces (fig. 4) are missing from the appliance. The ray is reflected on the sample and finally the image reaches the eye of the observer. It has a cherry wood case with two eyepieces and three numbered objectives: 2,6,7.

Bibliographic references.

48. a) Elemental chemical microscopy. Fig. 48. Leitz Metallurgical Microscope, described on page 86.
49. b) Stead J., WorkShop microscopes. J. Roy. Micro. Soc. 1909, 20, 22.
50. c) Tassin, The Microstructure of Cast Steels, J. Ind. Eng. Chem. 1913.5, 713.
51. d) Metallography applied to inspection, J. Ind. Eng. Chem., 1914,6, 95.