The Trials of Self-binding Harvesters at Chester. 719 
together by an axial spiral spring situated under the discs. 
While the knot is being tied the fixed end of the string is 
carried round towards the knotter, and by that means gives 
about If in. of yield during the knotting operation, and so 
relieves the stress on the string, which is said to enable an 
inferior quality to be used with safety. 
The several motions described are imparted at the proper 
action by the tripper arrangement described. 
The ejection of the finished sheaf is performed by a pair of 
prongs keyed on to the knotter spindle, which makes one revolu- 
tion to every sheaf that is bound. The compressor is held in 
position or lowered to allow the sheaf to be discharged by a 
rocking-shaft, which is brought into sharp motion by a lever 
actuated by a cam on the wheel to which the tripper pinion 
primarily gives motion. The outer end of this lever is connected 
