CLEARING LAND IN THE LAKE STATES. 7 
In cultivating a field covered with stumps, it is impossible to use 
modern farm machinery efficiently. Stumps are removed (1) by 
explosives alone, (2) by explosives used in connection with stump 
pullers or block and line, (3) by stump pullers alone, and (4) by 
power machines. 
EXPLOSIVES. 
Explosives alone are used effectively and economically in all stump- 
ing operations on the heavier soils and for well-decayed hardwood 
stumps on the lighter soils. They have the advantages of thor- 
oughly breaking up the stumps, of not requiring a large force of men 
for clearing operations or a large cash outlay at one time, and of 
enabling the work to be done quickly. The rather high cost of 
explosives when bought in small quantities and the fact that only 
experienced men should handle them are their chief drawbacks. 
Direct cooperative buying in wholesale lots will reduce materially the 
cost of the explosives. 
Satisfactory instructions * regarding the use of explosives are now 
published by practically all manufacturers. The chief faults of the 
average man in blasting stumps are his tendency to place the charge 
too‘shallow and his failure to put it under the center of resistance of 
the stump. | 
On most of the land-clearing operations in Michigan dynamite 
containing 40 per cent of nitroglycerin or its equivalent is used. In 
a few sections dynamite containing 20 to 30 per cent of nitroglycerin 
or its equivalent has been used with very satisfactory results. On 
the Pacific coast 20 per cent nitroglycerin dynamite or its equivalent 
is used almost exclusively. Dynamite containing the smaller per- 
centages is cheaper, less dangerous to use, and does not pack the soil 
to such an extent as the stronger preparations. On the heavier soils 
the lower strength explosives will give just as good results pound for 
pound as the higher. The lower strengths act more slowly, with 
much less shattering, and have almost the same lifting force as those 
containing higher percentages of nitroglycerin. 
It is commonly believed that dynamite with 60 per cent of nitro- 
glycerin is twice as effective as that with 30 per cent and that that with 
40 per cent of nitroglycerin has twice the effectiveness of 20 per cent. 
Tests by the United States Bureau of Mines? have demonstrated 
1 Valuable information regarding the proper use of explosives in stumping may be found in the following 
publications: 
McGuire, A. J. Land clearing. University of Minnesota Agricultural Experiment Station, Bulletin 
134, 32 p., 21 fig., 1913. 
Kadonsky, J. F. The use of explosives inclearing land. University of Wisconsin Agricultural Experi- 
ment Station, Bulletin 216, 19 p., 20 fig., 1911. 
Thompson, Harry. Cost and methods of clearing land in western Washington. U.S. Department of 
: Agriculture, Bureau of Plant Industry, Bulletin 239, 60 p., 25 fig., 1912. 
2 Hall, Clarence, and Howell, Spencer P. The selection of explosives used in engineering and mining 
operations. U.S. Department of the Interior, Bureau of Mines, Bulletin 48, 50 p., 3 pl., 7 fig., 1913. 
