THE WOOD AND ITS MECHANICAL PROPERTIES. 41 



so that the growth had become very slow. Under management 

 which should aim to secure rapid growth and strong wood the stands 

 should be thinned, and thus opened up. This means that after the 

 fiftieth year there would be fewer trees than is indicated in the table, 

 but their growth would be hastened. The total volume increase is 

 300 cubic feet each decade, or an average yield of 30 cubic feet a 

 year. This is a safe estimate for fully stocked stands on soils of 

 moderate fertility. Two sprout stands in Ohio 22 and 45 years old, 

 on very good soil, showed a yield of 44 cubic feet a year, while three 

 seedling stands 200 years old on river bottoms in the South showed 

 a yield of 36 cubic feet a year. The minimum yield from dry situa- 

 tions and on shallow soils was 15 cubic feet. There was no difference 

 discovered in the yields of shagbark, pignut, and mockernut. 



The fact that the heaviest yields were produced by stands of sprout 

 origin, while not conclusive, indicates that sprout stands may be 

 expected to produce heavier yields than seedling stands under short 

 rotations. This is ot great importance in deciding upon the method 

 of management. 



While conclusive figures on the yield of the important American 

 hard woods is lacking, there are enough to make general compari- 

 sons possible. Studies made by the Forest Service in Illinois show 

 that catalpa makes an annual average growth of 1.35 cords per acre; 

 black walnut, 0.90 cord; ash, 0.89 cord; and osage orange, 0.54 

 cord; in Maryland and Virginia, yellow poplar, 1.1 cords; and in 

 southern New England, chestnut, about 1 cord, and mixed oak and 

 chestnut sprouts from one-half to three-fourths of a cord. Catalpa, 

 moreover, is ready to market in twenty years, and chestnut in from 

 thirty to sixty. These figures are rough and must be taken with 

 considerable allowance, but even with due allowance the comparison 

 is very unfavorable to hickory, because the other important commer- 

 cial hard woods produce more merchantable material and some of 

 them mature in a much shorter time. 



THE WOOD AND ITS MECHANICAL PROPERTIES. 



The technical qualities of the wood are, in cases of the hickories, 

 of first importance. It is to its toughness, strength, and elasticity 

 almost entirely that the hickory owes its value. It is therefore im- 

 portant to know to what extent it is actually superior to other woods 

 like oak, maple, or eucalyptus, and also which of the different species 

 are most valuable, and under what silvical conditions the best timber 

 may be produced. It is also important to know the range of strength 

 and toughness of different kinds of hickory, so as to be able to dis- 

 tinguish good hickory from poor hickory by its physical character- 

 istics, and to know from what parts of the tree the best wood usually 

 can be secured. 



