Letter from Capt Sabine to Professor RenwicJc. 385 



Dr. Young has been recently confirmed by the experiments 

 of Professor Carlini on Mont Cenis. The amount of the co- 

 efficient, and consequently the value of the addition to be made 

 to the length of the pendulum determined by the experiments, 

 in order to reduce it to what might be supposed to correspond 

 to a pendulum vibrating seconds at the level of the sea, cannot 

 be otherwise in the present state of our knowledge than a 

 quantity arbitrarily assumed ; and it would, therefore, appear 

 to me preferable for the purposes mentioned in your report, to 

 take the pendulum of the place of observation, being the direct 

 result of experiment, in place of the pendulum at the level of 

 the sea, and thus to avoid the introduction of an arbitrary, 

 and therefore questionable, reduction. 



" Should this view, on this particular point, meet your con- 

 currence, the commencement of the second provision in your 

 proposed legislative enactment would run thus — (Journal of the 

 Institution, new series, No. I., pp. 114, 115) — * That the unit 

 of lineal measure shall be the yard, as used in this State at the 

 date of the declaration of its independence ; and that for its 

 more precise definition, and in order to its recovery in case of 

 loss, it is declared (until the measure of the pendulum shall 

 be transferred to some appropriate public building,) that the 

 said yard has been found, by experiments made with a pendu- 

 lum with a brass rod at Columbia College, New York, to bear 

 to the pendulum of that place, vibrating seconds in vacuo, at 

 the temperature of melting ice, the proportion of one million 

 (1,000,000), to one million, eighty-six thousand, one hundred 

 and forty-one (1,086,141).' 



" It is worthy of remark, that the acceleration between New 

 York and London, 41,85 seconds, which I trust is finally cor- 

 rected, is within one hundredth of a second of 41,84 seconds, 

 the number originally communicated in the spring of 1823 to 

 the Literary and Philosophical Society of New York, as the 

 result of my experiments, and printed as such in the volume of 

 their Transactions. It is almost unnecessary that I should 

 notice, that a difference of one hundredth of a second in 

 twenty-four hours is not a significant quantity in the proposed 

 legislative proportion of 1,000,000 to 1,086,141." 



