Royal Institution | 30th July 1856
My dear Sir,
If a straight line, or the edge of a white sheet of paper placed upon a black ground be
looked at through a glass prism with a small refracting angle, the refracting edge being parallel to the straight line; the latter, instead of appearing straight, will appear curved, turning its concave outline towards the edge of the prism. Hence, when two corresponding straight lines on two pictures intended for the stereoscope are brought into union by two such prisms, the coalescence of the lines, (rendered curved by the prisms) will give the appearance of curvity to the surface upon which the stereoscope image rests. What is true of the prisms is also true of the semilenses of the ordinary lenticular stereososcope,2 and the statement and explanation of the fact constitutes the major part of Mr Claudet’s paper. The circumstances are ingeniously varied, and the author also proposes stereoscopes by which the curvity of surface above referred to is abolished and a truthful flat surface obtained. The paper, in my opinion, is well worthy of a place in the Philosophical Transactions. The only qualifying remarks I have to make are the following:–
The principles of the stereoscope are already well known to those who have given due attention to what has been published on the subject, and to such persons, who do not need elementary instruction, Mr Claudet’s paper may appear prolix. The explanations are also given without any reference to the real authors of them, and it is a question whether some such reference may not be necessary to remove all just complaint on the part of those to whom we are really indebted for the theory of the stereoscope. The council will however have to consider whether the unfortunate personal differences to which the stereoscope has given rise, may not justify Mr Claudet’s reservation.3
I am dear Sir | very sincerely yours | John Tyndall
Prof. Stokes | Sec. R. S.
RS MS RR/3/79
The letter is annotated ‘Dr Tyndall’s Report on M. Claudet’s Paper’. Tyndall had delayed refereeing Antoine Claudet’s paper according to letter 1257. The paper was published as A. J. F. Claudet, ‘On Various Phenomena of Refraction through Semi-Lenses or Prisms, Producing Anomalies in the Illusion of Stereoscopic Images’, Roy. Soc. Proc., 8 (1856), pp. 104–10.
the semilenses of the ordinary lenticular stereoscope: The stereoscope is an optical device for combining photographs taken from points a little way apart to give the illusion of three dimensions. This can be done with mirrors (reflecting stereoscope) or lenses. In the latter refracting or lenticular stereoscope, the viewing lenses or eye glasses are called semilenses from the fact that they are segments (cut portions) of spherical convex lenses. Effectively they act as prisms.
Mr Claudet’s reservation: Tyndall was implying that Claudet might have deliberately avoided giving references to Wheatstone’s and Brewster’s publications on the stereoscope because of the feud between the two men over priority of discovery. In the paper eventually published, Claudet made no reference to the controversy, but this may have been because only an abstract of his paper was accepted.
Please cite as “Tyndall1264,” in Ɛpsilon: The John Tyndall Collection accessed on