SUE 



TABLE IT. 

 To reduce Customary Measure of 21 feet to a perch, to Statute. 



Er. 1. In 3fiA. lR. 10p. statute how many acres, &c. customary measure 

 of 21 feet to a per eh? 



Reduce to perches, which will be found 5810, .'. 5310 X 272,25 = 

 18ol772,50; this divided by 441 gives 3535,7 perches ; divide by 40 and 4 

 and the result is 22A.-1R. 26,7p. The same answer may be had from 

 Table I. 



E.r, 2. Reduce 22A. IR. 27p. customary, to statute measure. 



Here the number of perches is 3537, which, multiplied by 141, and di- 

 vided by 272.25, gives 3(>A. IR. 10p. The same result may be obtained 

 from Table II. 



II. Surveying TrigonometricaUy. 



1. These large surveys have been undertaken principally for the ac. 

 complishment of one or other of tbese three objects, viz. (1) For finding- 

 the difference of longitude between two moderately distant and noted 

 meridians, as the meridians of the observatories at Greenwich and Paris. 

 (2) For the exact determination of the principal place: in a country, with 

 a view to give greater accuracy to maps. (3) For the measurement of 

 a degree in various situations, in order to determine from thence the 

 figure and magnitude of the earth. 



These important objects can only be attained, by the greatest possible 

 degree of accuracy in the instruments employed, the operations perform- 

 ed, and the compatfttionjs required. 

 287 Q4 



