42 



THE ROYAL SOCIETY OF CANADA 



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R^.6. 



We know now that the axis ofxis (112 — 21)=81 cms. below the 

 iine LL, and it is now confirmed by finding whether the tension at 

 any point in the chain is equal to the weight of chain that would 

 reach from that point down to the axis of x. 



To do this, the spring balances are removed and cotton threads 

 attached to the half chain. Freely running pulhys, Pi, P2,were sup- 

 ported near A and B respectively. The thread ran over these pulleys 

 and supported free lengths of chain as shewn in Fig. 6. Care was 

 taken to get the threads tangential to the chain at A and B. The 

 vertical chains were adjusted in weight link by link until finally 

 the portion AB of chain was exactly in front of the right hand half of 

 the permanent chain hanging on the blackboard. D was made level 

 with B, and as it was impossible to get F level with A an extra three 

 inches or so of chain was hung from the top end F. It was then found 

 that H and E were at the same level. 



The total length of FH = 111 cms.; therefore, To=lll x -778 = 

 86 gms. 



The length of DE = 1923^ cms.; therefore Ti = 192'i^ x -778 = 

 150 gms. 



