Comparison of the calibrated integrated intensities of spectral lines emitted by the prominence. These intensities are plotted along the SoHO/SUMER slit for the part crossing the prominence (10−60″). The X-axis shows the position in arcsec along the SoHO/SUMER slit. We present the plots in linear scale to see the ratios of the intensities (left column) correctly and in logarithmic scale to better see the correlations between the curves (right column). Lyβ, Lyγ, Lyδ, Lyϵ, Ciii, and Sivi are obtained from SoHO/SUMER data. The Hα line was observed with Meudon/MSDP at 12:47 UT and is plotted with the SoHO/SUMER data only form 13:04 UT. The three raws correspond to different times of the SoHO/SUMER observations. For the Hα and Ciii lines (in linear plots) we used a scaling factor to properly place the curves within the graph.