An apparatus and process is provided for detecting elemental mercury in soil. The first image-forming unit includes an image pickup for picking up the optical image, an output unit for outputting the picked up optical image in digital image data, and a projecting unit for projecting the optical image on the screen in accordance with the image data output by the output unit. At least one of the first and second supports may also elastically support the motor, and may be a metallic leaf spring disposed within the throttle body. A radially inner located rotor can rotate relative to the axis of rotation and independently of both the stator and the outer rotor. The other of the first and second rollers advances the sheet. Varactor diodes and MOS varactors can be used as the variable capacitance elements.