The columns have marked entasis, and the flutings end in a semicircle, above which is generally a torus (always present in the so-called temple of Ceres).
In addition to magnesium and sodium the lines of potassium, lithium and also the carbon flutings exhibited in cometary spectra, has been seen.
The bands often appear in groups, and such spectra containing groups of bands when viewed through small spectroscopes sometimes give the appearance of the flutings of columns.
One practice which is especially prevalent, so as to strike every casual visitor, and dates from the early years of the empire, is that of filling up the flutings of the columns for about one-third of their height with a thick coat of stucco, so as to give them the appearance of being smooth columns without flutings below, and only fluted above.
The spectrum, which closely resembles that of a sunspot, is marked by flutings or bands of lines sharply bounded on the violet side and fading off towards the red.