CHAPTER II 

 SYSTEMS AND UNITS OF MEASUREMENT 



8. Systems of Measurement Used in Forest Mensuration. 



Throughout the United States and Canada the English system of 

 measure is used in all practical applications of Mensuration. In the 

 Philippines the metric system is the standard. (Appendix C, Table 

 LXXIX.) Efforts to substitute the metric system in the United States 

 for the units established by custom have so far failed, though its use 

 was sanctioned by Congress in 1866. Mensuration is applied more 

 generally to the solution of practical problems such as timber estimating 

 than to purely scientific research, and for the former, the results must 

 be expressed in the customary units to be intelligible. Scientific forest 

 measurements have also, except in a few instances, been expressed in 

 English units. 



In measuring distances and areas, the chain of 66 feet, or 4 rods, 

 is a commonly used unit. Five chains constitute a tally, or 20 rods; 

 and 16 tallies, or 80 chains, "equal 1 mile. One tally forms the side of a 

 square 2\ acres in area. Distances are commonly measured by pacing, 

 or counting the number of paces, the average length of the individual 

 pace having been determined by previous tests. A true pace is the 

 swing of one foot, or twice the length of a step. In counting, the pace 

 rather than the step should be used, since it reduces the count by half. 



The acre, containing 160 square rods or 43,560 square feet, is the 

 unit of area. In the rectangular system of survey adopted by the 

 United States the following definitions apply: 



Township — a tract approximately 6 miles square containing 

 36 sections. 



Section — a rectangular tract containing approximately 1 square 

 mile or 640 acres, but which may contain more or less 

 than this area in irregular surveys. 



Quarter Section — a subdivision of a section containing approxi- 

 mately 160 acres. 



" Forty " — a colloquial term describing a ^th section or quarter 

 of a quarter section containing approximately 40 acres. 



Lot — a tract ordinarily containing not less than 20 or more than 

 60 acres, but which may contain less area, of either 

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