Weights and Measures of New York. 103 



or new methods of division, for the several units of length, 

 weight, and capacity ; while, on the other hand, we learn that 

 slight modifications of the magnitudes of either of these, that 

 will render them more consistent with each other, and with a 

 standard existing in nature, if such be attainable, are perfectly 



(2.) It is a well-known and estabUshed physical fact, that the 

 pendulum vibrating seconds of mean time in any given place, 

 is invariable in length. That is to say, that if made of a sub- 

 stance susceptible of variation in length with changes of tem- 

 perature, the variation of its length will be attended with cor- 

 responding variations In the time of its oscillations ; while, if so 

 constructed as to remain invariable in length, the duration of its 

 vibration in very small circular arcs, and in an atmosphere of 

 unvarying pressure, will be constant : and although no experi- 

 mental pendulum is invariable in length under differing tempe- 

 ratures, nor the pressure of the atmosphere constant, yet these 

 two circumstances may be abstracted from, by means of cor- 

 rections deduced from accurate experiments on the law of 

 expansion by heat, and on the buoyancy of the atmosphere. 

 The length of the seconds pendulum varies with the change of 

 latitude, according to a regular and well-known law ; and it has 

 lately been shown to be affected by local circumstances. Still, 

 however, the length of the seconds ppndulum in a given posi- 

 tion, when corrected for changes of temperature, and atmos- 

 pheric pressure for the magnitude of its arc of vibration, and 

 reduced to the level of the sea, is a standard, determinate and 

 invariable in its dimension, that does exist in nature : it is also 

 determinable, without any great difficulty, by persons furnished 

 with the proper instruments, and possessed of the requisite 

 scientific knowledge. For the best methods of determining the 

 length of the pendulum, the world is indebted to Borda and 

 Kater ; and the method of the last is more especially remark- 

 able as one of those brilliant discoveries that mark eras in 

 science, and confer immortality on their inventors. The pen- 

 dulum then should be recognised in the revised laws as the 

 instrument whereby the standards may be restored, if lost ; and 

 with whose dimensions they are to be at present compared, by 



