Sentence:  These improvements consist, firstly, in a novel construction of apparatus to be attached to or applied upon railways, at those parts termed switches, <WSD>shunts</WSD>, or moveable rails, which are commonly used for transferring engines, carriages, or trains, from one line of rails to another, as occasion may require, and which apparatus I call a "switch or <WSD>shunt</WSD> protector." 
Meaning of the word marked with <WSD> tags:  A switch on a railway used to move a train from one track to another.