II. The effect of pressure upon arc spectra. No. 3. -Silver, λ 4000 to λ 4600. No. 4. -Gold

Abstract

1. Preliminary . —The effect of pressure upon arc spectra was first investigated by Humphreys and Mohler, and later by Humphreys. They found that, in general, the lines broadened, were displaced towards the red end of the spectrum, and showed a greater tendency towards reversal. Humphreys’ work has dealt more fully with metals other than silver, of which the following table comprises all previous measurements under pressure:— The following investigation was undertaken for the purpose of extending the work to higher pressures. The spectrum of the silver arc has been photographed under pressures ranging from 1 to 201 atmospheres in the region λ = 4000 to λ = 4600 Å. U.