The reaction, also called the Goldschmidt process, is used for thermite welding, often used to join railway tracks. Thermites have also been used in metal
Hartridge smoke meter: A light source and photo-electric cell mounted facing each other on swinging arms. Movement of the change-over knob alters their
shear stress, force tending to cause deformation of a material by slippage along a plane or planes parallel to the imposed stress. The resultant shear is of