Small amounts of very dense matter in the central engine of an active galaxy have an important effect on the emitted spectrum at ultraviolet and longer wavelengths. If only 0.1 per cent of the total matter expected there is in the form of small dense clouds, then much of the infrared and optical spectrum is absorbed and reradiated in the ultraviolet. Such clouds thereby suppress much of the primary synchrotron radiation emitted by relativistic electrons in the strong magnetic field which is responsible for accelerating them. The magnetic field supports and confines the dense clouds in a manner analogous to prominences above the solar photosphere. In this paper we discuss the properties of the clouds and show that they are a likely constituent of the central engine.
