120 



UNIVERSITY OF COLORADO 8TDDIE8 



In this case the value of ic=p is 



as is also seen from Fig, 8, in which *r=iQ Aj^rOA.^— OQ =r-- 



Fig8. 



and also x=Q^^ — A^B^z=W — r^. From this figure it is apparent 

 that during the motion the following groups of parallel links are 

 maintained: — 



A,BJiOAJ|A3B„ 



BAIIOA3IJB3A. 



A.B,!;0A,||A3B„ 

 BAIJOAJIBA, 

 It follows from this that during the motion 



B,B=A,A=BB3, 

 and B,B,=AA3=B,B3. 



Consequently, the points BjBjB^B^ always form a parallelogram, in 



which QB,=QB3=QB3=QB^. 



But B,B3=QB,+QB3, 



and B,B=QB,+QB^, 



hence BiB=B,B^. 



The parallelogram has, therefore, equal diagonals, and is a rectangle. 

 The closed link-work is, consequently, also completely determined by 



