new standards of weights and measures. 3 



seconds at various stations, from Unst to Formentara, are 

 there detailed. In these experiments M. Biot employed the 

 method of Borda, which requires that the absolute length of 

 tlie pendulum should be obtained by actual measurement at 

 each station. M. Biot's observations and mine, both at 

 Unst and Leith Fort, were made at the same stations ; and 

 M. Biot found, from the mean of fifty-six series, using 

 different measuring rods and various pendulums, the length 

 of the second pendulum at Unst to be ,994943083 metres, 

 and at Leith Fort ,994524453 metres. 



Converting these results into inches of Sir George Shuck- 

 burgh's scale, by taking the length of the metre at 39,37079 

 inches, as given in the Philosophical Transactions for 1818, 

 we have the length of the seconds pendulum at Unst, after 

 reduction to the level of the sea, 39,17176 inches, and at 

 Leith Fort S9A55S9 inches, the first differing from my 

 determination +,00029, and the latter —,00015 of an inch. 

 The difference of results obtained by methods totally dissi- 

 milar being so small, and with contrary signs, it may be 

 reasonably inferred from them, as well as from what has 

 been before advanced, that the length of the pendulum 

 vibrating seconds in London has been determined to within 

 one ten-thousandth of an inch of the truth. 



From the near agreement of the results of the French and 

 English experiments on the length of the pendulum, it may 

 be inferred that the length of the French metre, expressed in 

 parts of Sir George Shuckburgh's scale, is probably not 

 erroneous one ten thousandth of an inch. 



From an account recently published by Captain Sabine, 

 F. R. S. of his valuable experiments for determining the vari- 



