28 REPORT— 1839. 



veiling rate'' differs from the mean '■^stationary rate" in the same way, 

 or the losing rates were increased, and the gaining ones diminished. 

 Whether, however, we use the travelling rate or the stationary rate for 

 the determination of the difference of longitude of the two places, we 

 we obtain results extremely near to each other, provided we take the 

 means between the outward- and the homeward-bound determinations. 

 This was shown by calculations submitted to the Section. Taking the 

 first result, or that given by the travelling rate, as the true difference 

 of longitude between the Observatories of Brooklyn and Greenwich, 

 and applying the quantity, 4'09 sec. for the difference of meridians be- 

 tween the Observatory of Brooklyn and the City Hall, in New York, 

 we have for the difference of longitude between the latter place and 

 Greenwich 4^^ 56^ 7^'08 west. The longitude of NewYork from Paris, 

 as given in the Connaissance des Tems, by M. Daussy, is 5^ 5™ 22*'0 : 

 if from this be deducted 9"" 2P'28, the difference of longitude between 

 Greenwich and Paris, as determined by the chronometrical experiments 

 made by me between those two places in 1 837, we shall have 4*^ 56^ 

 0^.72 as the difference of longitude, according to that observer, between 

 Greenwich and New York. 



Comparison of Results. 



First, by the chronometers, the longitude of New York is h. m. s. 



west from Greenwich 4 5Q 7'08 



Second, by M. Daussy, as given in the Connaissance des 



Tems 4 56 0-72 



Difference 6-36 



This difference is little more than one half of a mile in longitude ; 

 and the smailness of it proves that this, {the first result by the transit 

 of chronometers from England to America,) removes the apprehensions 

 which have been suggested that chronometers may not go well in 

 steam-vessels. 



Note, by Mr. Dent, accompanying a Table of the Hate of the Transit- 

 Clock in the JRadclyff Observatory, Oxford, was then read. 



In 1S38 a transit-clock was made by Messrs. Arnold and Dent for the 

 Radclyff Observatory, Oxford, to which, by the special desire of the late 

 Professor Rigaud, was attached the improved mercurial pendulum with 

 its cistern of cast iron, &c. In the statement now submitted of the going 

 of this clock will be found, said Mr. Dent, a mean daily rate, which, 

 when corrected for an intentional over-compensation, has been rarely 

 equalled ; the amount of the correction for this over-compensation is, 

 I think for many reasons, a subject for experiment alone : I conceive 

 it cannot be calculated but with extreme difficulty — 1st, because the 

 centre of oscillation must be disturbed, and then an additional correc- 

 tion becomes necessary, in consequence of the alteration in the pendu- 

 lum-rod to bring it to time ; 2nd, because some quantity is due to the 



