PLANTING 75 



gone over several times. Perhaps the subsoil plow may be of some 

 advantage, especially in preparing the land deeper for the planting 

 of the trees. 



If planting follows the plowing immediately, three or four men, 

 or men and boys, can be used to advantage — one to distribute the 

 trees and prune the roots ; another to hold the trees and line them 

 up in one direction, and later to stamp in the soil over the roots ; 

 and a third to line up the trees in the other direction and shovel 

 the soil around them. 



As soon as the trees are planted, the furrows may be filled in 

 with the aid of the plow, care being taken not to injure the trees 

 or throw them out of line, or they may be left to be leveled by 

 cross-cultivation during the summer. 



Digging holes by dynamite. Recently the use of dynamite for 

 digging holes has become more common, but it is not always ad- 

 visable to employ it. Generally speaking, where the soil is hard 

 or the subsoil is clayey or hard and impervious, dynamite may 

 well be used, but it is not needed for sandy or open topsoil or sub- 

 soils. To obtain the best results from dynamite, the operator should 

 have a clear understanding of the principles of blasting. 



The following discussion of the principles of blasting and the 

 use of dynamite is based on that of the E. I. Du Pont de Nemours 

 Powder Company. 



Principles of blasting. When dynamite explodes, it is changed 

 into a very large volume of hot gases, which exert a strong pushing 

 force equally in every direction, because they require a much larger 

 space than the dynamite which produced them. If the dynamite is 

 shut up in a space just large enough to hold it, that is, if it is closely 

 confined before it is exploded, the gases, in escaping, force out 

 and carry along with them the material which shuts them in. 



These gases, pressing equally in every direction, will escape 

 principally where there is the least pressure opposed to them, 

 that is, along the lines of least resistance, and will force out the 

 material confining them more in that direction than in any other. 

 If the back pressure is about the same at the top and on all sides, 

 then they will carry with them, or break up as they escape, a large 

 amount of the material which shuts them in ; but if one place in 

 the earth or rock around them is much weaker than all the rest, 



