xxxvi 



Introduction to the Makeestoun Observations, 1844. 



sions or 4', aud the periods of the cross passing the wire, are estimated to a tenth of ;i 

 second (See Table 12, Introd. 1843, p. xxxix.) The arc of vibration at the com- 

 mencement was measured by means of the right micrometer, it was usually taken 

 very small on account of the difference in the times of vibration with difference of 

 arc (afterwards noticed, 54), although it is now certain that large arcs of vibration 

 give a time which satisfies better the previous equation and the true coefficient of 

 the instrument. 



The following Table contains the observations for the value of T made in 1844. 



The number of vibrations observed, is given in the column after that contain- 

 ing the arc of vibration at commencement. 



Table 5. — Values of T, the Time of Vibi-ation of the Balance Needle in a Vertical 

 Plane, with the Temperature of the Needle. 



