1. Proc. Roy. Akad. Amsterdam, vol. xxvii. Nos. 1 and 2; NATURE, vol. 113, No. 2846, p. 716; C.R. Acad. Sc. t 178, p. 1153.
2. Spectra with larger dispersion were obtained about the middle of March.
3. It remains still to be shown that the bands in blue-ultraviolet are not produced by, canal rays., either retrograde rays or rays produced by imperfect rectification of the current.
4. W. H. Keesom and H. Kamerlingh Onnes, Proc. Roy. Akad. Amsterdam, 24, p. 1315.