Abstract: The present invention is a relatively narrow tool carrying self-propelled machine that is particularly configured such that it can easily move through narrow mines while supporting any one of several tools. In one embodiment, the self-propelled machine is designed to be powered totally or substantially totally by an emulsion fluid that is readily available in mines.

Abstract: The present invention is a relatively narrow tool carrying self-propelled machine that is particularly configured such that it can easily move through narrow mines while supporting any one of several tools. In one embodiment, the self-propelled machine is designed to be powered totally or substantially totally by an emulsion fluid that is readily available in mines.

Abstract: A rear screen optic projection apparatus is provided having a multiple mirror reflection system mounted in a supporting enclosure and adapted for utilization with photographic projection equipment such as slide projectors and motion picture projectors. The reflector-type optic system of this apparatus includes three mirrors which are angularly displaced with respect to each other for providing a substantially long optical path from the projector to a viewing screen. The supporting structure is designed with a viewing screen and an entrance aperture for an image to be projected along the optical path. A plurality of the apparatus in a stored configuration by covering the viewing screen and closing the entrance aperture.