Auroræ: Their Characters and Spectra

This work surveys historical and contemporary observations of polar lights, offering detailed descriptions of their forms, colours, heights, durations, and occasional sounds, and illustrates many examples. It examines correlations with magnetic disturbances, solar activity, atmospheric electricity, ozone, meteoric dust, and related phenomena such as zodiacal light, lunar auroral patches, and the solar corona. The author presents spectroscopic measurements, compares auroral lines with laboratory discharge spectra, discusses competing theories of origin, and reports experiments demonstrating magnetic effects on electrical discharges, accompanied by drawings and chromolithographs.