LAUSR

In this article I address the unsolved problem of how the eighteenth-century optical machine generated an illusion of spatial depth and why variations of the apparatus continued to be produced well into the twentieth century when it should have been superseded by technically superior devices such as the stereoscope. I trace, across a diverse constellation of artefacts, design themes and variations that I take as evidence of embedded artisanal knowledge. Optical machine design was inconsistent with eighteenth-century optics, as exemplified by the camera obscura and linear perspective. It reflected an emergent paradigm according to which the forms of the external world are projected by the mind upon incomplete sense data-a process of world-production that philosophers were attempting to explain using metaphors of optical devices like the concave mirror and theater stage. My emphasis on asynchronous progress is a corrective to Jonathan Crary's Foucauldian model of homogenous, successive "scopic regimes."