Jules Janssen's ‘Revolver Photographique’ and its British Derivative, ‘the Janssen Slide’

Abstract

The first practical device for sequential photography, invented to record the transit of Venus in 1874, was later recognized as the precursor of the movie camera. At least technically much more successful than is usually thought, Janssen's 'revolver photographique' was only grudgingly tolerated by the French authorities in 1874, but it was widely adopted in modified form by the British; the story is told in the light of the holdings of the Royal Observatory Greenwich manuscripts, now in Cambridge University Library (CUL), and of the Institut de France Library (ldFL) manuscripts, Paris.After the failure of the telescopic observations of the transits of Venus of 1761 and 1769, due to the notorious 'black drop effect',I the technical advances of the late nineteenth century made it seem that photography and clockwork could solve the difficult problem of timing the contacts precisely. This belief, and the pressing need to refine the determination of the mean Sun-Earth distance, now referred to as 'the astronomical unit', explain why the numerous expeditions mounted to observe the 1874 and 1882 transits comprised what was probably the biggest international effort ever made to observe a single astronomical phenomenon.' In all the great seafaring countries, dedicated committees wrote endless reports to define the best strategies and to devise the most appropriate techniques to obtain objective and permanent records of the event. In 1874, there were at least 62 parties from ten or so countries sent to some 80 locations.' Instruments had been carefully chosen and standardized in order to make all the parties' observations comparable, at least among observers from the same country. There have been various studies published recently on the transits of Venus" and on the astronomical unit problem.' The leader of one of the French expeditions was the ruggedly individualistic and stubborn French physicist, photographer" and inventor, Jules Janssen , who planned to take to Japan, in addition to the 'official' instrumentation, extra telescopes of his own design, together with a repeating photographic device, the 'revolver photographique'. Jimena Canales has published a detailed analysis of the scientific and political context of the use of the 'revolver' by the French;' the object of this article is to describe how the principle of Janssen's instrument was applied to versions made in England and widely used by the British expeditions. It is clear that the British astronomers placed more reliance on the principle of the so-called 'Janssen-slide' or 'Janssen' than did their French counterparts.

The black-drop effect explained

“…Unfortunately, the widely-reproduced plate of his observations is not of the actual transit but rather of a previous test (Fig. 7), as shown by Launay & Hingley (2005). They showed that it was first published in 1891 and then reproduced in Janssen's Oeuvres Scientifiques of 1929.…”

“…16. Reports from observers all over the world indicate that the black-drop effect was less prominent than had been expected, though such comments had also appeared in reports of the 19th-century transits (Launay & Hingley 2005). Since prior knowledge showed that the black-drop effect was not intrinsic to Venus but was rather a combination of instrumental effects and effects to some degree in the atmospheres of Earth, Venus, and Sun, it is no surprise that the better telescopes we have now, since the time of Captain Cook, provide cleaner images and potentially less black drop.…”

‘The memory of life itself’: Bénard’s cells and the cinematography of self-organization

“…So, it is most surprising that there is so little memory remaining from Bénard's cinematographic work. The chronophotography allowed no more than an analysis of fleeting dynamic phenomena at a more leisurely pace, just like Jules Janssen's had wished to do when he invented the photographic revolver that is the ancestor of cinema (Canales 2002(Canales & 2006Launay & Hingley 2005). The cinematograph, on the other hand, was designed to recreate the studied phenomenon: "giving the observer the faculty of seeing again the scene that he studies as many times as necessary" (Anonymous 1909, p. 682).…”

Jules Janssen, the Birth of Solar Physics, the Foundation of Meudon Observatory, and the Mont Blanc Adventure (1875-1895)

“…Janssen was elected in 1873 at the French Academy of Sciences. He was the inventor of the photographic revolver (Launay & Hingley, 2005) to record the Venus transit observed in Japan in 1874, and more generally to produce motion pictures of dynamic events. The revolver may be considered as a remote ancestor of the cinematograph.…”