168 ELEMENTARY FORESTRY. 



clothing and other purposes; the fruit and leaves, which are also' 

 used for food, medicinal and chemical extracts. 



Wood is Made up of Cells which vary in form and in 

 arrangement in different species. The cells are arranged in the 

 form of irregular concentric cones, so that a cross section of a 

 tree shows a series of concentric rings. For ordinary purposes, 

 however, a log may be considered as being made up of a series 

 of concentric cylinders, each cylinder representing one year's 

 growth. If each ring is examined closely, it will be noticed that 

 it is made up of an inner, softer, lighter-colored portion and an 

 outer portion that is firmer and darker colored. The inner por- 

 tion was formed in the early part of the season, when growth 

 was rapid; this portion is termed the spring wood. The outer 

 portion, where the cells are packed firmly together, grew in 

 the summer, when the growth was slow, and this is termed the 

 summer wood. Since the latter portion is very heavy and firm, 

 it to a large extent determines the weight and strength of the 

 wood. 



Wood a Structure. On account of the peculiar arrange- 

 ment in its structure, wood should not be regarded as a homo- 

 geneous mass, but rather as a mechanical structure, the arranp-*- 

 ments of the units of which in each case should be carefully con- 

 sidered in estimating its strength and its value for various pur- 

 poses. 



Methods of Sawing. In sawing wood the relation of the 

 saw cut to the annual rings is an important matter, and its ref- 

 erence in relation to them has given rise to the names cross- 

 cut, tangential and quarter-sawing. 



CrosS-Cut Sawing simply refers to cutting across the grain. 

 This method of sawing is seldom adopted other than for pur- 

 poses of division, but occasionally it is used for making thin 

 veneers, which are used in finishing panels and the like. 



"Through and Through," or regular sawing, refers to the 

 ordinary way of sawing lumber, in which most of the cuts are 

 tangential to the annual rings. 



Quarter-Sawingllis sawing that is done perpendicularly to 

 UK- annual rings of the wood. Wood thus sawed presents an 

 evenness of grain not to be found in wood tangentially sawed. 

 When cut nearly or quite on tin- radius tlu- beautiful silver grain 

 of some woods is thus shown t<> ilu- lu-st advantage. 



