Sentence:  [W]hen a transverse, or, within certain limits, an oblique impulse, impinges laterally upon a continuous mountain range, two movements of vibration are communicated; the one, a wave transmitted along and in the line of the axis, the other a transverse wave, which causes the axial line to sway laterally, and transmit a "quam prox." horizontal transverse wave, along from one end to the other; like the <WSD>sinuous</WSD> movement which travels along a long rope when, hanging suspended between two points at the same level, it is jerked suddenly at one end, transversely to its length. 
Meaning of the word marked with <WSD> tags:  Having curves in alternate directions; meandering.