30 



a surve}" of Egj-pt and are e8tal)li.shing monuments in some cases. It 

 is doubtful whether these will have any great permanent value as they 

 are not tied to guide meridians or standard parallels. The laek of 

 monuments in the surveys of the villages makes it necessary for the 

 farmers in the districts inundated to resurvey their lands after each 

 subsidence of the water. A few permanent monuments may alwa3's 

 be found in the villages and from these the rest of the land is laid out. 



The work is repeated until a majority are satisfied that the land has 

 been properl}^ measured. It would cost the farmer only 5 or 10 

 cents per stone to establish permanent monuments at the corners of 

 his farm, })ut so fixed has become the custom of remeasuring the land 

 each year that it is preferred to a more convenient system. 



English engineers in the survey department are handicapped not 

 only by their inabilit}^ to secure the best kind of assistance in the field, 

 but ))y existing survej^s recognized by the native farmer. His ances- 

 tors measured land to their satisfaction, and he is content to follow 

 their example, not oidy in the surveys but in the computation of field 



Fui. -'i. — l)iiigram showing inaccuracy of land measurements. 



notes. The Egyptian has a special formula for computing the area of 

 land to which he adheres with a steadfastness which would be praise- 

 worth}- in a better cause. For instance, when a triangular piece of 

 ground is to be surveyed, only the lengths of the sides are taken. To 

 compute the area the lengths of two adjacent sides are added, the sum 

 is divided by 2, and this quotient is multiplied by the length of the 

 remaining side divided b}- 2. If the figure happens to be a quadri- 

 lateral, the two opposite sides are added together and divided by 2 

 and the quotient is multiplied by the two remaining sides added 

 together and divided by 2. Putting the formula in figures and refer- 

 ring to the accompanying diagram, the inaccuracy of the method may 

 be plainly seen (fig. 5 ). 



, ab -f be ac 

 Area or triangle = ^ X -^ 



■ ,. T ., , ab-fcd ac + bd 

 Area ot quadrilateral = ^ — X — ^ — ■ 



