88 CAPTAIN SABINE ON THE DIFFERENCE IN THE VIBRATIONS 



the rate of an invariable pendulum between the Royal Observatory and 

 Mr. Browne's house in London ; the pendulum vibi'ating quicker in Greenwich 

 than in London. 



The retardation computed for the difference in latitude between the two sta- 

 tions is 0.15 of a vibration per diem, and for their difference in elevation being 

 about 50 feet and employing Dr. Young's co-efficient of .6, is 0.12 of a vibration 

 per diem. The sum of the two computed retardations is 0.27 ; which added 

 to the acceleration 0.48 shown by the experiments, makes altogether 0.75 of a 

 vibration per diem ; by which amount the result of experiment differs from 

 what would have been anticipated, supposing that no previous experience 

 had existed of the occurrence of such anomalies. 



With regard to the fact, of the existence of this irregularity between Green- 

 wich and London, it is one which admits of easy verification by persons who 

 may be disposed to repeat the experiments : the stations are convenient and 

 close at home ; and the magnitude of the irregiilarity is such as to preclude 

 uncertainty, since with proper precautions, it is not difficult to determine the 

 relative rates of an invariable pendulum to nearly |th of the present irregu- 

 larity. 



With regard to its cause, — having already expressed the opinion that I had 

 been led to form on the occurrence in my former pendulum experiments, of 

 what I believe to have been irregularities of a similar nature, — it is unnecessary 

 now to repeat that opinion ; and having since seen no occasion to alter it, on 

 the contrary much to confirm it, I gladly leave the discussion to others whose 

 opinions are entitled to more weight. 



