27 



uncertainty existed respecting the true longitude 

 of Ferrol, the centre of which town is 10' 20" 

 east of the Tower of Hercules at Corunna. An 

 occultation of Aldebaran, and a long series of 

 eclipses of Jupiter's satellites, observed by Ad- 

 miral Mazarredo, and calculated by Mechain, 

 seemed to prove that, in the maritime atlas of 

 Tofino, which is in other respects so accurate in 

 the indication of partial distances, the determin- 

 ate positions of Corunna and Ferrol were inex- 

 act by two or three leagues. My time-keeper 

 confirmed these doubts respecting the opera- 

 tions of Tofino. I found* the observatory of 

 the Admiralty at Ferrol 0 h 42' 21" west of Paris. 

 The mean of all the observations made by the 

 Spanish astronomers, and lately published by 

 Mr. Espinosa, gives 0 h 42' 25". I have already 

 observed, that several expeditions having set 

 sail from this last port, the false position, which 

 has been laid down, has had a disadvantageous 

 influence on the longitudes of several towns of 

 America, determined not by absolute observa- 



* Observat. Astron. Introd. p. xxxvi, t. i, p. 24 et 33. 

 Espinosa, Memorias sobre las observaciones astron. hechas 

 por los navegantes espanoles, 1809, t. i, p. 23. If we sup- 

 pose, that my chronometer did not augment it's diurnal re- 

 tardation during the passage from Madrid to Corunna, which 

 would be contrary to direct experiments made at Marseilles, 

 the longitude of Ferrol will still be 23" of time more than 

 that at which it is fixed by Mr. Tofino. 



