46 



the ietigjjh of line ■was, «iy, "9 ohains, the iramter of trees could at once be f onnd &s 

 follows :— 



rnmber of trees in crop of 6 acres ^^ 6 acree 

 number counted on 1* chains of Hue "" 0*9 acres 



The following rules* should also be ohserved in the 

 case of sample plots. Their application to linear surveys 

 need not he discussed. 



(1) No sample plot should be selected on the edge 



of a crop ; for a trae average will seldom be 

 found there. 



(2) On slopes presenting a wide range of elevation, 



or in crops offering a great variety of aspects 

 and soils, several sample plots judiciously dis- 

 tributed should be selected. 



(3) The form of the plots should be regular : in gene- 



ral the best shape is that of a long rectangle. 



(4) The aggregate area of the sample plots should 



not be less than 5 per cent, of the total area 

 of the crop or type of growth of which they 

 are chosen as the pattern. 



(5) In mature crops no sample plot should usually 



be less than from 3 to 6 acres in extent ; and in no 

 case should the area be less than one acre, 

 except, perhaps, in young uniform crops. 



(6) In crops of considereble extent several plots 



should be taken and not one of largre size. 



Size-classes of the trees enumerated. — Whether the trees 

 are counted over the whole area or only on portions of it the 

 number to be measured is so great that it is not practicable 

 to record the correct diameter of each individual stem. 

 Trees of more or less the same sizes are, therefore, grouped 

 together in girth or diameter classes. 



Where, as often happen;;, timber is sold by, and tables are prepared for, girth 

 measureinente, the classification might with advantage be by girths ; the calipers used 

 being marked bo as to indicate girths not diameters. 



The range of girth or diameter included in each class 



* NoTB.— These rales, and Biiich of what follows in this chapter, have been extracted 

 from the " Treatise on the mensuration of timber ard timber crops," cnmpiled from the 

 German hyMt. P, 3, Carter, asd obtaioable at the office of tha Sapexinteadent, Goveriiment 

 Printing, India, 



