A stress apparatus is reported which allows us to apply forces up to 300 N to solids perpendicular to the field in a superconducting magnet. This configuration is necessary to study stress dependences of transverse magneto-transport effects and magneto-optical properties in Faraday geometry. The usefulness of the apparatus is demonstrated by Hall effect and transverse magnetoresistance measurements in n-InSb as well as far-infrared cyclotron resonance experiments on n-Ge.