File:James Green & James H. Gardiner - Skiagraph of a Nautilus pompilius - Proceedings of the Malacological Society of London - Vol. II, Pl. XV, p. 178.jpg

English: James Green & James H. Gardiner - Skiagraph of a Nautilus pompilius - Proceedings of the Malacological Society of London - Vol. II, Pl. XV, p. 178.

The accompanying text (on page 179) reads: "Mr. J. Green and Mr. J. H. Gardiner exhibited a series of skiagraphs of Molkisca taken by the Röntgen-rays, which were commented on by Mr. B. B. Woodward.

The examples shown were obtained by means of a Crookes tube (focus pattern), actuated by a powerful induction coil giving 8 in. sparks, and the exposures varied from a few minutes for a large Clausilia to a little more than an hour for Nautilus pompilius.

In all the Gastropods the columella was distinctly shown up to the very apex, with all twists and plaits on it, the latter being perfectly marked, even through the shelly pillar, as in Voluta; the clausium was indicated in Clausilia, as well as the various folds, and the notches in the margins of the plates of Cryptoplax were rendered visible through the substance of the girdle. A group of shells taken with fragments of calcite and aragonite made it clear, by the opacity of the minerals, even when thinner than the shells and far more transparent to ordinary light, that the passage of the X-rays through the shells must be due to the presence of the organic matter in their substance.

A close inspection of the skiagraphs revealed the fact that they faithfully reflected the different relative thicknesses of the shell substance interposed between the tube and the photographic plate. Hence the external ornamentation is reproduced, and even, as in the case of the Nautilus (selected for reproduction here, PI. XV), the lines of growth; whilst in this instance, too, the varying degrees of solidity of the siphuncle, and the point of attachment of the shell-muscle, are well brought out."