Hittorf examined the phenomena exhibited in so-called high vacua, that is, in exceedingly rarefied gases.
Frederick Slare noticed that the luminosity increased when the air was rarefied, an observation confirmed by Hawksbee and Homberg, and which was possibly the basis of Berzelius's theory that the luminosity depended on the volatility of the element and not on the presence of oxygen.
Electrical studies, however, engaged most of his attention, especially in connexion with the theory of the voltaic cell and the electric discharge in rarefied gases.
Ciii.) he published the first of his classical researches on the action of the magnet on the electric discharge in rarefied gases.
The heights of peaks determined by exact processes of trigonometrical observation are bound to be more or less in error for three reasons: (1) the extraordinary geoidal deformation of the level surface at the observing stations in submontane regions; (2) ignorance of the laws of refraction when rays traverse rarefied air in snow-covered regions; (3) ignorance of the variations in the actual height of peaks due to the increase, or decrease, of snow.