384 Letter from Capt. Sabine to Professor RenwicJc, 



esteemed to have gone in the account of the penduhim experi- 

 ments : and the number of vibrations in a vacuum, in twenty- 

 four hours of mean solar time, at a temperature of 62°, should 

 be of pendulum No. three 86113,14 instead of 86113,19, and 

 of pendulum No. four 86122,73 instead of 86122,78, as given 

 in the 9th column of page 236 of the Pendulum Experiments. 



" An accidental error of far greater magnitude has occurred 

 in the summary of the results in the same page, in taking 

 86118,48 instead of 86117,98, as the mean of the above 

 numbers, representing the vibrations strictly comparative with 

 the number 86159,79 at London. This error does not exist 

 in the separate account which I drew up of the experiments 

 at New York, and which is published in the transactions of the 

 Literary and Philosophical Society of that city*. 



*' The number of vibrations at New York strictly comparative 

 with 86159,79 at London, including the small correction for 

 the level, is then 86117,94 ; and the length of the seconds' pen- 

 dulum, in the room at Columbia College in which the experi- 

 ments were made, 39,10107, presuming the length in Mr. 

 Browne's house in London to be 39,13908 inches. 



" The height above the sea of the room in which the experi- 

 ments were made at New York being 67 feet, this length would 

 require to be increased 00025, in order to obtain the length of 

 the pendulum vibrating seconds at the level of the sea, pre- 

 suming the reduction to be proportional to the squares of the 

 distances from the earth's centre. The discussion of Dr. Young 

 in the Philosophical Transactions for 1819, had, however, 

 shown that this proportion can be in no case just, requiring 

 always to be diminished by a co-efficient, varying in regard to 

 the form and density of the materials composing the elevation 

 on which the experiments were made ; and the reasoning of 



* " A similar error occurs in the same summary, in taking the mean 

 of the vibrations of the two pendulums at Hammerfest, 86216,09 and 

 86225,83, and which ought to have been 86220,96 instead of 86221,46 ; 

 and the resulting pendulum 39,19468 instead of 39,19512. I mention 

 this, because they are the only errors of consequence to correct, that 

 have yet come to my knowledge in the account of my pendulum experi- 

 ments, and I will beg you to do me the favour of correcting them in the 

 copies in the libraries of Columbia College, and of the Literary and 

 Philosophical Society ; with one other, with respect to the Magnetic Dip 

 at Ascension, p. 474, which is printed South, when it should be North." 



