269 



Art. IX. A Letter relating to Mr. Watts' Remarks on 

 Captain Kater's Experiments, &c., addressed to the Editor 

 of the Quarterly Journal. 



Sir, 



I AM tempted to give you the outline of an article in the 

 second Number of the Edinburgh Philosophical Journal, by a 

 Mr. William Watts, of the Custom-house, Penzance, entitled, 

 " Remarks on Captain Kater's paper, containing experiments 

 for determining the length of the seconds pendulum in the 

 latitude of London." 



The writer begins by mistaking the length of the secojids pen- 

 dtdum for that of the pendulum of experiment ; and in conse- 

 quence arrives at the conclusion, that the number by which the 

 square of the arc of vibration is to be multiplied " is incorrect," 

 and should have been 1,645 instead of 1,635, the number given 

 by Captain Kater. 



He next convicts Captain Kater of not having expressed the 

 number of vibrations made by the pendulum in 24 hours, beyond 

 the nearest hundredth of a vibration. 



He then proceeds to point out, that Captain Kater has com- 

 mitted an error in his computation of the correction for the 

 buoyancy of the atmosphere in one of the 12 series of experi- 

 ments, to the amount of txvo hundred thousandths of an inch. 

 This being divided by 12, might occasion an error of about two 

 millionths of an inch, in the length of the pendulum vibrating 

 seconds. And lastly. 



He asks, " why cannot the disappearance of the disk" (in the 

 observations of coincidences), " be noted to a quarter of a 

 second, as readily as an entire second ;" or, in other words, why 

 cannot an object be seen through a telescope when it is not in 

 the field of view ? 



I am. Sir, 



Your obedient Servant, 



and constant Reader, 

 October, 1810. Z. 



