146 ENGLISH WOODLANDS 



of trees in the wood. This method of estimating 

 the number of trees is founded on the fact that 

 there are 4,840 yards in an acre, which is taken 

 to be equal for practical purposes to 4,900, 

 i.e. 7 x 7 x 100. Also one or more fairly large 

 sample plots, of which the size is accurately 

 known, may be selected and the trees in them 

 counted and the result multiplied by the fraction 

 which the selected portion bears to the area of 

 the whole wood as shown by the ordnance map. 



One source of error in an estimate is that a 

 wood is usually not uniform in growth. A 

 small difference in the distance at which the 

 trees stand apart means a great difference in 

 their number ; the portions selected may not 

 be really representative. Another source of 

 error is that it not easy to know what deduc- 

 tions for blanks should be made from the acreage 

 within the wood fences. Roads, paths, and 

 bare spots when added together may be an 

 appreciable portion of the whole area. 



An error in an estimate is easily made, and 

 disputes are very probable unless the trees are 

 counted or great care is taken in forming an 

 estimate. It is possible that a landowner may 

 advertise a wood as containing about 20,000 

 trees, and a timber merchant, after buying it 



