Hirst and Wood 'The Natural Stereoscope'

deluxe version of the large box-type viewer built by John Hirts and Joseph Wood, mounted on a central brass post which rises from a burl wood stand with four decorative arms. The technical design is as remarkable as the cabinetry: the large diameter, achromatic lenses are adjusted for interocular distance by rotating the large horizontal bar over the eyepiece, focus is adjusted by the knurled knob beneath the main housing that drives a rack and pinion assembly which shifts the position of the slide holder. A hinged door at the right side opens for inserting and removing slides. A unique feature is the inclusion of two sets of rollers which hold translucent, tinted filters for altering the light cast on the slide. The carved wooden arms and the decoration on the top have very skilfully been replaced, otherwise in good original condition. Only a handful examples of the Natural Stereoscope are known to exist - this certainly is the most desirable of all early stereoscopes.