136 



Dr. Watson on the Determination of the 



range over a very considerable time, the dates of the various 

 measurements o£ period are given to indicate the constancy 

 which can be obtained with such a quartz-fibre suspension. 







No. 1. 





Date. 



Period. 



13. 



x.03. 



3-6615 



14. 



x. 03. 



11 



26. 



x.03. 



10 



27. 



x.03. 



11 



19. 



xi. 03. 



09 



25. 



xi. 03. 



12 



26. 



xi. 03. 



13 



2. 



xii. 03. 



14 



21. 



i.04. 



11 



5. 



ii. 04. 



11 



5. 



ii. 04, 



11 





Mean. 



. 3-6612 



No. 2. 

 4-0543 





Mean. 



43 





. 4-0543 





No. 3. 







3-7672 







70 





Mean. 



69 





. 3-7670 





No. 4. 







3-7751 







48 







48 





Mean. 



. 3-7749 



No. 5. 



Mean.. 



Mean. 



Mean.. 



Mean 



3-7726 



23 



22 



. 3-7724 



No. 6. 



37467 



71 



. 3-7469 



No. 7. 



3-7545 



47 



45 



49 



. 3-7547 



No. 8. 



3-7421 



22 



24 



24 



.. 3-7423 



Mean.. 



No. 9. 



3-7446 



47 

 49 



48 



. 3-7448 



No. 10. 

 3-6682 

 81 

 83 

 86 

 84 

 84 

 81 

 81 



Mean... 3"6683 



Cradle only. 



1-2427 

 9 



6 



5 

 2 

 2 

 5 

 6 



Mean... 1-2425 



If h is the period with a bar of moment of inertia K^ in 

 the cradle, while t is the period of the cradle alone, K being- 

 its moment of inertia, we have 



Ki + K 





where c is a constant depending on the suspension fibre. Hence 



Kq c 



tS-t Q '-±7?' 



Thus if the bars are uniform in density and diameter we 



