1. Discovery of small ions;Elster;Physik. Zs.,1899
2. The scheme for designating units suggested by Benndorf, H., , , Physik. Zs., 25, , 60 ( 1924, ) is here used; the electrostatic or the electromagnetic system is designated by the suffix es or em, respectively.
3. Pollock, A., , , Phil. Mag., , 29, , 514– -526 and 636–646 ( 1915, ); see also below.
4. Nolan, J. J., , , R. K., Boylan, , , and G. P., de Sachy, , , Proc. R. Irish Acad., A, , 37, , 1– -12 ( 1925, ). J. Scholz, Zs. Instrumentenk, 51, 505–522 (1931).
5. For more detail see Israël, H., , , Beitr. Geophysik., , 40, , 29– -43 ( 1933, ).