the expected unequal impressions, two sensibly identical images were obtained. I believe this failure, unique, be it remarked, to be due to an insufficient regulation of the spark, which, doubtless, was not sensitive. Fig. 6 is a photo-engraved reproduction of the prints obtained with and without "N" rays issuing from a Nernst lamp.
Fig. 7, similarly, shows the result of an experiment with "N" rays, produced by two large files.
Though the photogravures are far from rendering in a satisfactory manner the aspect of the originals, they nevertheless show the influence of "N" rays on a photographic impression.
I give further (Figs. 8 and 9) the reproduction of photographs, showing that "N" rays, issuing from a Crooke's tube, are polarized.
These photographs date from the month of April, 1903. They were not obtained by the method of reiterated alternation of exposure, as this method is difficult to apply to this case; but the experiments have been repeated a great number of times with the most minute
