40 



THE ROYAL SOCIETY OF CANADA 



Therefore as P travels outwards from N the point N traces a 

 curve (the tractrix) such that the length of the tangent to the catenary 

 included between the catenary and the tractrix is equal to the length 

 of chain from A to P. Also the tangent to the tractrix is of constant 

 length. 



Experimental Treatment 



In the experiment to be described the chain known to the trade 

 as Jack Chain No. 14 was employed. Its linear density is very uniform, 

 averaging about -778 gms. to the centimetre. It was hung from two 

 nails, B and C (Fig. 4), driven into a blackboard, on the same level 



fo 6o uo zo a io 4^ &o fo foo /zo om 



Fig. 4- 



and 260 cms. apart. In all the diagrams the chain is represented by a 

 heavy line. The length of the chain was 322 cms. A level line, LL, 

 was drawn of the blackboard at a convenient distance below A (the 

 position of this line was conditioned by the height of the table top in 

 front of the board). Ten centimetre distances were marked out on 

 this from O' to the right and to the left and by means of a plumb 

 line hung over the points the ordinates of the chain above the tempor- 

 ary axis LL were measured. Care must be taken to measure to the 

 middle of the chain. The values obtained are given in Table I. 



