fIGURE OF THE EARTH. 331 



the author to observe the latitude of Arbury Hill, as he would 

 then have two partial arcs independent of the whole and of each 

 other. 



For determining the angular extent of these arcs, Lieut. Col. Facts. The 

 Mudge observed the zenith distances of several stars on the offi^e^ircswere 

 meridian above the pole, by means oi a large zenith sector observed by 

 constructed by R msden, with the same pains that he h^^^ w-'th t^zemtU 

 bestowed upon the theod(j]ire Lieut. Col, Mndge paid ail sector ; 

 possible attention, and took rsil such precautions as might natu- 

 rally be expected from an ob-server of his experience and 

 address. Nevertheless the results of his observations made '" wl^'ch the 

 on different stars, differ no less than 4 seconds from each gg^. 

 other. But, by taking a mean of all, the dimensions of the 

 three arcs reduced to the centre at each station are as follows. 



Between Clifton and Dunnose 2° 50' 23",35 Means of ob- 



Clifton and Arbury 1 14 3 ,40 servation in 



Arbury and Dunnose 1 36 19,95 deg.andpts. 



The extent of the first arc, in linear measure, is ]036339| 

 feet English, and when this is reduced to toises, we have for 

 the lengths of the three arcs from Lieut. Col. Mudge's mea- 

 sures^ 



From Clifton to Dunnose 1 62067,3 The same arc* 



Chfton to Arbury 70380,2 in toises : 



Arbury to Dunnose 91687,1 



These last values exceed those resulting from my compu- 

 tations, the first by 10 toises, the second by 2, the third by 8 

 toises ; and these differences arise from the convergence of 

 the meridians, which the author thought might safely be neg- 

 lected, and in fact it does not make a difference that is percep- 

 tible in the value of a degree upon the meridian. For the 

 difference of 8 toises, in the distance between Dunnose and 

 Arbury, makes but 5 toises difference in the value of a degree 

 upon that arc, and the difference of 10 in the whole distance 

 from Dunnose to Clifton, makes 3| in the measure of each 



degree on that arc. So that, as far as this source of disagree- 



• 1 !. .1 > w J • ij ^ are not materr. 



mentis concerned, the authors results and mine would not ^iiy differino- 



be found to differ materially from each other, from the com. 



puted tablet. 



But, 



