The History and Present State of Discoveries Relating to Vision, Light, and Colours, Plate II

“Plate II” features seven illustrations to accompany the sections of Priestley’s text, entitled “Period I: The Revival of Letters in Europe,” and “Period II: From the Revival of letters in Europe to the discoveries of Snellius and Descartes.” Figure 10 illustrated a parabolic mirror or burning mirror, the type of which was used to light fires in ancient times by focusing the sun’s rays; Priestly notes, “this was the form of mirror with which Archimedes burned the Roman fleet” (History and Present State, 14). Figure 11 is a diagram of a convex lens used for magnification as an optical phenomenon. Figure 12 illustrates the anatomy of the human eye, explicating the components essential to “this instrument of vision” (J. Priestley, History and Present State, 32). Figure 13 is a diagram demonstrating how light passes through the eye, using the “crystalline humour” as the lens that focuses the light on the retina (J. Priestley, History and Present State, 34). Figure 14 is a drawing of a room-sized camera obscura in which the image outside the chamber is shown projected, inverted, on the wall of the room after passing through a small aperture with a lens (J. Priestley, History and Present State, 37). Figure 15 is an illustration, copied from Kircher’s Ars Magna Lucis et Umbrae (1646), of a polished hollow cylinder. An image placed at the bottom of the cylinder will appear “like a real solid substance, suspended within the mouth of the vessel” (J. Priestly, History and Present State, 47). Figure 16 tracks “the progress of a ray of light in the formation of a rainbow” (J. Priestley, History and Present State, 52).

Priestley received the LL.D. degree of Edinburgh University on December 4, 1764 and was elected a Fellow of the Royal Society on June 12, 1766. In addition to the publication of The History and Present State of Discoveries, Priestley also received the Copley Medal from the Royal Society in 1773 for his paper “Observations on Different Kinds of Air,” published in the Philosophical Transactions of the Royal Society (R. Schofield, “Priestley, Joseph”).

Theologian, natural philosopher, dissenter, and polymath, Joseph Priestley situated this work within a centuries-long lineage of observation and experimentation in the natural sciences. He considered this text the first volume of his intended, extensive work to be entitled The History of all the Branches of Experimental Philosophy; the work was ultimately not completed due to his increasing preoccupation with the Unitarian ministry and the tumult created by his theological and political beliefs, including the Birmingham Riots of 1791 and his eventual emigration to the United States (R. Schofield, “Priestley, Joseph”).

For the first volume of this comprehensive history, Priestley “chose the history of optics, on which there was abundant information” published on the topic from which he could draw; however, unlike Smith’s A Compleat System of Opticks, published thirty-four years earlier, Priestley was unable to elucidate the subtler mathematical supports for optical physics (R. Schofield, “Priestley, Joseph”). In its discussion of the accomplishments of ancient Greek and Roman mathematicians and natural philosophers, the findings of Alhazen (Ibn al-Haytham) and other “Arabian Philosophers,” as well as those advances made by Kircher, Roger Bacon, Giovanni Battista della Porta, Newton, and others, Priestley’s The History and Present State concretely connects optics to an emerging, Romantic sensibility concerned with history. The Romantic consciousness conceived of history as an organic, continuously unfolding process and “believed in the reality and diversity of human experience rather than the uniformity of universal abstractions” (A. Kennedy, “Historical Perspectives in the Mind of Joseph Priestly,” 173).

As with many of the images in this gallery, “Plate II” from The History and Present State juxtaposes precise diagrams explicating optical physics with illustrations of instruments used for optical amusements and illusions (like the camera obscura), suggesting Romanticism’s wide-ranging preoccupation with vision. Priestley acknowledges the historical presence of the camera obscura, crediting Della Porta with “the invention of the Camera Obscura, which furnishes one of the most amusing and pleasing experiments in the whole compass of opticks” (J. Priestley, History and Present State, 34); he also notes, however, that Della Porta overlooked the possibility of using the device to draw “with great exactness” (37). This observation of Priestley demonstrates his own awareness of the instrument’s numerous, potential uses for both optical experimentation and recreation.

The camera obscura illustrated on “Plate II” (Figure 14) is an entire room, in which an observer could obscure him or herself in order to view the inverted, projected image created within. This is an early version of the camera obscura that effectively illustrates the way in which the apparatus disembodies and interiorizes vision (J. Crary, Techniques of the Observer, 39). However, the variety of other optical devices that are juxtaposed with the camera obscura on “Plate II,” including explorations of light and illusions, denies the camera obscura’s singular status. This straight-forward arrangement of optical interests challenges Crary’s assumption that the camera obscura was the sole model of vision in the Romantic period, later replaced by models which privileged “the process of perception itself” over the camera obscura’s inflexible and static mode of vision (J. Crary, Techniques of the Observer, 137-138).