390 ME. J. J. MANLEY: OBSERVATIONS ON THE 



decay in the amplitude is very low ; hence it is not difficult for an observer, using a 

 telescope, to obtain data for the determination of the RP. during any period of the 

 8 to 10 minutes which immediately follow the release of the beam. By continuous 

 observation we are, therefore, able to accumulate sufficient data for some 18 or more 

 independent determinations of the R.P. before the amplitude of the oscillations 

 becomes too small to yield trustworthy results. 



In calculating the 11 P. from the data, we may take successive pointer readings in 

 groups of three or five. As it appeared that the use of small, rather than that of 

 large, groups would yield the desired information with the greatest degree of 

 certainty, it was decided to calculate the KPs. generally from groups of three 

 observations. 



We here give typical data obtained by employing a No. IF Bunge balance, the 

 beam of which was solid and 13 cm. in length, and a load of 20 gr. We may 

 mention that this is but one taken from some scores of similar examples. 



TABLE I. 



