Sentence:  Where the wind-trunk is short between the reservoir and wind-chests the tone will be steady; but when it is long, and with bends, the elasticity of the air causes an unsteadiness in the tone, which must be obviated by the use of "concussion-bellows", sometimes called “<WSD>winkers</WSD>,” or by an elastic diaphragm. 
Meaning of the word marked with <WSD> tags:  A small bellows in an organ, regulated by a spring, controlling variations of wind pressure.