Solar Microscope
   "The solar microscope is in reality a magic lantern illuminated by the sun's rays; it serves to produce highly magnified images of very small objects. It is worked in a dark room: [the drawing at the right] represents it fitted into the shutter of a room. 
   The sun's rays fall on a plane mirror, M, placed outside the room, and are reflected toward a condensing lens and from thence to a second lens by which they are concentrated at its focus. The object to be magnified is at this point; it is placed between two glass plates... The object thus strongly illuminated is very near the focus of [positive] lenses which forms upon the screen at a suitable distance an inverted and greatly magnified object. 
   As the direction of the sun's light is continuously varying, the position of the mirror outside the shutter must also be changed, so that the reflection is always in the direction of the axis of the microscope. ...
The object is usually attained by inclining the mirror to a greater or less extent by means of an endless screw, and at the same time turning the mirror itself round the lens. 
   The solar microscope furnishes the means of exhibiting to a large audience many curious phenomena, such, for instance, as the circulation of blood in smaller animals, the crystallisation of salts, etc." From Ganot's Physics (Longmans, Green, and Co., London, 1883) pp 541-542

   The solar microscope and accessories at the right were made by Jules Duboscq of Paris, and were delivered to Vanderbilt University in 1875 and 1876. This form of the apparatus, often called a Port-Lumière, was invented by the father of Jules Duboscq in 1838. The 1885 Duboscq catalogue lists the complete set of apparatus at 500 francs ($100). 

   The apparatus also included a Nicol prism for the study of polarized light. 

   At the left is a solar microscope at the Royal Scottish Museum in Edinburgh. When I took this picture in 1978 I omitted to record any data from the accompanying placard, but it strongly resembles the solar microscope at Kenyon College (below), which is marked "Benj. Pike & Son. New York". Since a Scottish instrument is very unlikely to have been made in New York, it seems clear that Pike put his name on an import. D. J. Warner of the Smithsonian ("Projection Apparatus for Science in Antebellum America", Rittenhouse, 6, 87-94 (1992), has suggested that it was possible for the Pikes to have assembled the apparatus from imported parts. 
   The solar microscope below, labelled in flowing script with the Pike name, is in the apparatus collection at Kenyon College in Gambier, Ohio. A blank bill of lading for the Port of New York from the 1840s, used as a space-filler behind the mirror, supports the Warner hypothesis that this apparatus was built by Pike from imported parts.
   The solar microscope, its accessories and the storage box pictured at the right are from Grinnell College in Iowa. This apparatus looks much the same as the two examples above from Scotland and Kenyon College, suggesting that it was made in Europe and imported into the United States. 

   The solar microscope was invented ca.1740. Its popularity began to wane when intense artificial sources of light (such as the lime light, zircon button light, and the oxyhydrogen light began to be available after the middle of the nineteenth century.

   The solar microscope at the left was bought by Prof. Frederick Barnard of the University of Mississippi in the second half of the 1850s from the firm of Lerebours et Secretan of Paris. It cost 300 francs, or about $60.

   The apparatus is now at the Unversity Museum. 

   Jack Judson of San Antonio prefers to call this apparatus by the name Port Lumiere, as it was not configured to project microscope slides. 

   It was made by McIntosh Battery and Optical Company of Chicago, and is in the Jack Judson Collection at the Magic Lantern Collection in San Antonio, Texas.

   The apparatus is beautifully displayed in a specially-made window of birdseye maple.

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