60 



Length of zinc 

 increased. 



COMPENSAtlOJI PENDULUM. 



Increased the compensation for heat and cold, 6 holes 

 — 4} inches, or, the length of the zinc rod to 25 inches. The 

 clock was again set to mean time. 



Rate of going. 



July 1 



0" 



26 



^0" 36 



27 



— 9-3 



13 



— 0* 21 



Aug. 9 



— 12- 



7 



— 0* 31 



16 



— 14- 2 



28 



— 0- 34 



Sep. 13 



— 24- 



12 



— 0* 80 



25 



— 35* 5 



22 



— 0- 84 



Oct. 17 



— 52- 1 







IProper length 

 ©f zinc. 



Although a thermometer was attached to the clock, I 

 could not from a necessary attendance to business register 

 it regularly; the difference of its height in March and June 

 may be taken at about 22 degrees, and in July and Octo^ 

 ber 14> without much errour. 



On comparing it with the rate of the clock, the compensa- 

 tion, in the latter case, appears nearly as much too great, 

 as it was in the first too small. The true length of the 

 zinc rod ought to be about 23 inches. 



The length of the zinc rod, thus ascertained, is 1| inch 

 more than the experiment by the lamp makes it; indeed, I 

 have always suspected there might be some errour in that 

 experiment, on account of the length of the arc of vibration 

 being affected by it. 



Having no means of finding the time accurately but by 

 equal altitudes, I could not get so many observations as 

 might be wished. I trust, however, these will not be founi 

 altogether useless. 



I am Sir, 



Your obedient servant, 



HENRY WARD. 



IX. 



