180 
Scientific Intelligence. 
ascertain it, with sixteen watches, in the summer of 182S ; and 
a remarkable circumstance occurred, which was not within the 
object of his original mission. For, in going from Greenwich 
to Falmouth, a difference of longitude was found equal to 
20' 11". 49; and, in returning from Falmouth to Greenwich, a 
difference of 20' 11 ".13. Now, the difference, as determined 
from the Trigonometrical Survey (given in the third edition of 
the requisite tables), is only 20' 6".9 ; and this variation made 
it expedient to engage Dr Tiarks to verify his observations in 
the Channel. He was furnished with twenty-nine, chronometers, 
and was employed from the latter end of last J uly till the middle 
of September in sailing between Dover and Falmouth. His re- 
sults are as follows : 
Longitude of Dover station, 
Portsmouth Observatory, 
Pendennis Castle, 
Madeira, 
Qh 5' m54 E. 
0 4 24.77 W. 
0 20 10 .85 W. 
1 7 39 .08 W. 
From hence it is clear that the figure of the earth must be 
somewhat different from that assumed for determining the lon- 
gitudes from the Trigonometrical Survey, and that about 5" 
must be added, in the latitude of the Channel, for every 20' of 
longitude which is deduced from it. 
4. Reported Inaccuracy of M. BesseTs Catalogue. — A report 
relative to an inaccuracy in M. Bessel’s Catalogue having not 
only gone abroad, but having found a place in the Annals of 
Philosophy for November, p. 397, we are happy to have it in 
our power to contradict this rumour by the following ex- 
tract of a letter, from M. Bessel, to a gentleman in I^ondon : 
— “ With respect to my Catalogue of the declination of the 
principal stars, I think the information you sent me must be 
founded on some misunderstanding, as I have not the least suspi- 
cion that it is wrong. The effect produced by the bending of 
the telescope of my circle appears to me to be so well deter- 
mined, that on this point I can expect no further improvement, 
without running the risk of greater inaccuracies. In my method 
both of observation and computation, I have never neglected any 
thing that could have any influence of consequence. I cannot, 
therefore, throw any light on what you mention, unless some one 
would point out inaccuracies at present unperceived b}' me, 
