a) Schematic view of the Norma spiral arm tangency. The emissions (distinguished by color) tracing the spiral arm are shown as a cross cut of the layers from the inner to outer edges (adapted from Figs. 2 and 3 in Vallée 2014a). b) A sketch indicating the velocity (V_LSR) structure of the corresponding spectral line intensities near the tangency for each layer. Note that this cartoon is intended to be a schematic and is not to scale.