Mr Galbraith on tie English Arc of the Meridian. 269 



III. General Remarks. 



Computing the co-ordinates of Leithhill from Eater's new survey, rela- 

 tive to the meridian and perpendicular to the meridian of Greenwich, and 

 also those from the same point from Dunnose by the data given in the 

 Trigonometrical Survey, I have found the difference of latitude, between 

 Greenwich and Dunnose, to be geodetically . — 0° 51' 34" .80 S. 



Latitude of Greenwich by observation, . . 61 28 38 .50 N. 



Latitude of Dunnose geodetically, . , 50°37' 4".20N. 



Latitude by Eater's observations, . . . 60 37 5 .27 

 Latitude by Bessel's Z sector observations, . 60 37 6 .85 



Mean of these three, 50° 37' 6" .44 N. 



which, from their close agreement, must be very near the truth. 



From the same co-ordinates, the longitude geo- 

 detically, is, 1°11'51".5GW. 



Longitude by Trigonometrical Survey, . . 1 11 3G .00 W. 



Difference, 15" .Sg"" 



or about 13' in a degree. 



This error arises from slight inaccuracies in the data as- 

 sumed and methods then practised, but which, by Colonel 

 Colby, the present conductor, have been long ago abandoned. 



It is much to be regretted, indeed, that the later results and 

 observations have not hitherto been published, for it would be 

 very desirable that every thing connected with the Survey, 

 like the astronomical observations made at the Royal Obser- 

 vatory at Greenwich, and other places, should be annually 

 published at the public expense, since they are undoubtedly 

 public property, and the results would enable civil-engineers, 

 and private amateurs, to reap all the advantages justly expected 

 from so valuable a source. 



From calculation I have found the station at Clifton 4737.59 

 feet west of the meridian of Dunnose, v/hen the arc is deduced 

 from the azimuth at Dunnose ; while, from the azimuth at Clif- 

 ton, the arc passing through that station is 4909.95 feet west 

 of Dunnose, or conversely, the station at Dunnose is 4909.95 

 feet east of the meridian of Clifton. Now, if all the opera- 

 tions and observations have been accurately performed, espe- 

 cially those to determine the azimuths, these numbers ought 



