REVIEWS AND NOTICES OF BOOKS. 87 



theories dealt with are in many cases equally applicable to 

 British forests, and the book will undoubtedly rank as a 

 valuable contribution to what the authors describe as the 

 ever-growing English literature in forestry. 



The authors define forest mensuration as that branch of 

 forestry which deals with the volume of stands, trees, logs, 

 and other timber products, and with the study and yield of 

 trees. The units of measure that may be employed are : the 

 board foot, cord, cubic foot, standard, linear foot, or sometimes 

 in the case of poles, posts, railway ties — the piece. The 

 contents of a log in board feet may be expressed by log 

 scales based on empirical data or by mathematical formulae 

 such as the formula — (0.7854 D- x H x 12) -r 144 board feet, 

 which expresses the board foot contents of a cylindrical log 

 when no allowance is made for slabs, kerf, or other losses. 

 The instruments commonly used in measuring standing trees 

 are calipers and hypsometers of various descriptions. The 

 authors recommend the use of the Biltmore stick — a graduated 

 rule, the graduations of which indicate the diameter of the 

 tree at the point measured when the rule is held tangentially 

 to the tree — for general work not requiring extreme accuracy, 

 in preference to the calipers. By taking advantage of various 

 mathematical formulae for the frustrum of solids, and considering 

 the tree not as a whole but as composed of several parts 

 or sections, stump, logs, tops, the contents of felled trees can 

 be computed very accurately. When the tree is measured 

 as a whole and not in sections, Schiffel's or Pressler's formula 

 enables the volume to be ascertained with considerable accuracy. 



Volume-tables are very frequently used in the United States 

 and in Canada for ascertaining the volume of standing trees, 

 and the authors' description of volume-tables in chapter vii. 

 describes clearly how they are constructed and utilised. A 

 volume-table is defined as a tabular statement showing for a 

 given species the average contents of trees of different sizes. 

 Volume-tables may be made for any unit of volume : board 

 feet, cords, standards, cubic feet and so forth. The tables 

 may be based on diameter only, or as is more usually the 

 case, on diameter and height — the total height or the merchant- 

 able height. They may also be based on diameter and number 

 of logs of standard length or on diameter and tree-class. The 

 usual custom in constructing volume-tables is to follow the 



