312 LOGGING 
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 stimip. 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. 
The holes in which the explosive is placed are best bored by 
a 2-Lnch 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. Dynamite, in exploding, 
tends to exert an equal force 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 1-foot deep for all stumps 1 foot or less in diam- 
eter, and proportionall}' deeper as the diameter increased. 
Holes are charged, primed and tamped in a manner similar 
to bore holes in rock. Enough explosive should l^e 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 jMinnesota 
required from one-half to eight, 40 per cent djTiamite cartridges, 
the average number being three per stump. 
The DuPont Powder Company recommends, in general, a 
charge of 1^ pounds of 20 per cent dynamite for each foot in 
diameter of stump, up to 4 feet; above this diameter 2^ pounds 
per foot in diameter. 
On dry ground one man can bore holes, load, and blow out 
an average of fifty stumps per daj^, if they are not widely scat- 
tered. 
^ See Minnesota Fanner's Institute Annual, No. 21, 1908. 
