Memoir of the late Francis Baily, Esq., F.R.S., Sfc. 53 



received the most unremittirii^ attention from Mr. Baily, as 

 well as from every other member of the committee, in all its 

 stages. To him also was confided the task of drawing up the 

 final report of the committee appointed to carry out the wishes 

 of the Admiralty, which will be found in the fourth volume of 

 our Transactions, and which is a model of good sense, clear- 

 ness, and lucid arrangement. The report was immediately 

 acted upon by government, and the result was the present 

 British Nautical Almanac; a work which, if it continue to be 

 carried on, as I trust it ever will, on the principles which pre- 

 vailed in its reconstruction, will remain a perpetual monument 

 to the honour of every party concerned in it. 



The Pendulum. — The seconds-pendulum having been con- 

 stituted the legal source from which, in the event of the loss 

 of the national standard of length, the yard might at any time 

 be recovered, it may be easily imagined with what intensity of 

 interest the announcement was received among all conversant 

 with these fundamental determinations, that a very material 

 correction had been entirely overlooked in the reduction of 

 the experiments, on which the Act of 5 Geo. IV. c. 74 was 

 founded. This correction is, in fact, no other than the cor- 

 rection due to the resistaiice of the air, and, placed in this 

 light, it would seem somewhat wonderful that such an over- 

 sight could have been committed ; but it had been customary 

 to consider the effect of resistance on the time of vibration to 

 be wholly confined to its influence in diminishing the arc, and 

 this secondary effect being allowed for in the formulae em- 

 ployed to compute what is called the correction for the arc of 

 vibration, the primary or direct effect of resistance dropped 

 altogether out of notice, or, rather (owing to an entire mis- 

 conception of the nature of the mechanical process by which 

 resistance is operated), had been supposed to be altogether in- 

 appreciable in its amount. The real effect of resistance, though 

 under a somewhat confused statement as to its nature, had, 

 however, been long before noticed, and its amount even as- 

 certained with tolerable correctness by the Chevalier Buat, in 

 1786; but his experiments and theory had so entirely fallen 

 into oblivion as to have escaped the notice not only of Captain 

 Kater, but of his own countrymen, Borda and Biot, and were 

 unknown even to Bessel himself, who, in 18'i8, rediscovered 

 the correction in question, and, for the first time, made it an 

 integrant feature in the modern system of pendulum reduc- 

 tions. The light in which this correction was placed by Buat, 

 and even in some respects by Bessel, tended not a little in my 

 opinion to obscure the clear perception of its nature, by repre- 

 senting it as due to a certain portion of air adhering to and 



