RAILROAD CONSTRUCTION 277 



Cypress stumps have many lateral roots and since they 

 usually grow on mucky soil they are difficult to blow out. A 

 quick powerful explosive, such as 60 per cent dynamite, is recom- 

 mended by manufacturers. The common practice with swamp 

 species is to place a §-pound cartridge under each large lateral 

 root, and 4 or 5 pounds under the center of the stump. The 

 charge is then fired with an electric blasting machine. 



Stumps with defective centers often split apart and allow the 

 force of the explosive to pass upward without blowing out the 

 roots. This can be obviated by placing a chain around the top 

 of the stump. 



Where a right-of-way must be cleared of stumps, it is easier 

 to blow them out before the tree is cut because the weight of 

 the crown helps to pull out the roots. 



The holes in which the explosive is placed are best bored by 

 a 2-inch auger welded to a 5-foot iron rod that has a ring on the 

 upper end through which a round stick can be inserted for a 

 handle. 



. The depth of the charge below the stump should be governed 

 largely by the size of the stump itself. Dynamite, in exploding, 

 tends to exert a force equally in all directions. When placed 

 under a stump the soil below the charge offers greater resistance 

 than the soil above and the force is exerted upward in the form 

 of an inverted cone. Consequently the deeper the charge is 

 placed the wider the cone at the surface of the earth. 



A rule^ followed with success in Minnesota was to place the 

 charge at least i-foot deep for all stumps i foot or less in diam- 

 eter, and proportionally deeper as the diameter increased. 



Holes are charged, primed and tamped in a manner similar 

 to bore holes in rock. Enough explosive should be placed under 

 the stump to remove it at the first shot, because it is difficult 

 to make an effective blast in loosened dirt. 



One thousand stumps, ranging from 18 to 48 inches in diam- 

 eter and averaging 30 inches, which were blasted in Minnesota 

 required from one-half to eight, 40 per cent dynamite cartridges, 

 the average number being three per stump. 



1 See Minnesota Farmer's Institute Annual, No. 21, 1908. 



