466 EDITOR'S NOTES. 



curacy may be the most open to question. The value 

 O s '43, as the equivalent of a change of 1 of Fahr. in 

 the temperature of the pendulum, was obtained in 

 the experiments of 1824, by the comparison of vibra- 

 tions in temperatures which differed from each other 

 nearly the whole amount of the range of the natural 

 temperatures experienced at the several stations, and 

 measured by the same thermometers. But as those 

 experiments were made in the middle of a London 

 winter, the high temperatures were necessarily produced 

 by heating the apartment by artificial means ; and al- 

 though this was done with great care, and in many 

 respects under very favourable circumstances, it is 

 always difficult to maintain for many hours an artificial 

 temperature, exceeding that of the atmosphere by little 

 less than 40, so as to be quite sure of a correct mean 

 temperature. For this reason I was glad to have an 

 opportunity of examining the question afresh in 1829 

 1830, by experiments made at the Royal Observatory at 

 Greenwich (with the permission of Mr. Pond, then astro- 

 nomer royal,) with a pendulum similar to those I had 

 previously employed, and with the same thermometers, 

 in natural temperatures varying about 32 of Fahr. from 

 each other. These are recorded in the Phil. Trans, for 

 1830, art. xix. They gave the value corresponding to 

 1 of Fahr. 8 -44 instead of O s -43, the latter having 

 been obtained from the comparison of the vibrations in 

 the natural and artificial temperatures. In submitting 

 the experiments of 18291830 to the Royal Society, I 

 expressed my own preference for the value, O s -44, ob- 

 tained when both the extremes were natural tempera- 



