an altar so constructionally erected that it might serve for two chapels. In some old examples a pierced screen divided it from north to south, in which case the two officiating priests would have faced each other had they celebrated contemporaneously. In most cases, however, the division was made by a screen which stood east and west, that is, supposing the altar to have been placed in its customary position. A double altar still exists, and in used at Bologna, without any screen to separate, it; at which altar the officiants face the congregation.