Abstract: A process for dewatering sludges, which comprises performing a first stage agitation of the sludge to be dewatered during addition of a first high molecular weight flocculant developing in an aqueous solution an electric charge in polarity opposite to that of the sludge to effect neutralization of the electric charge of the sludge, conducting subsequently a second stage agitation of the sludge during a further addition of a second high molecular weight flocculant developing in an aqueous solution an electric charge in polarity opposite to that of said first flocculant to cause flocculation of the sludge and subjecting the so flocculated sludge to a dewatering operation, wherein a flocculant composed of a natural high molecular organic compound or a derivative thereof is used for at least one of said first and second flocculants with simultaneous employment of high power agitation for said first stage agitation, which process obtain a dewatered cake having low moisture content with efficient dewatering of the

Abstract: A shutter speed setting and display apparatus for use with a single-lens reflex camera comprises a shutter speed variation apparatus, a shutter speed setting apparatus and a shutter speed display apparatus. The shutter speed variation apparatus produces count signals and applies the signals to the shutter speed setting apparatus for setting the shutter speed and, as the shutter speed display apparatus, a digital display apparatus can be employed, which displays either a shutter speed set by the shutter speed variation apparatus or a shutter speed determined by an automatic exposure measurement circuit or both. To this shutter speed setting and display apparatus, a flashlight source detecting apparatus and a shutter speed restricting apparatus can be attached for restricting the shutter speed to be set by the shutter speed which is to be set by the shutter speed variation apparatus in a synchronizing range of the flashlight source with a shutter of the camera.