SILOS, ENSILAGE AND SILAGE. 69 



from sap-wood. Green lumber should never be used, as 

 it is more liable to decay, and, moreover, when the usual 

 preservatives, petroleum or roofing pitch, are applied, 

 disappointment in the results will probably follow. 

 Among the precautions to secure durability, the liberal 

 und judicious use of petroleum and roofing pitch or tar, 

 may be urged as of the first importance. 



The manner in which these preservatives are applied 

 is a matter of no little consequence, if the best results 

 are to be obtained. When applied boiling hot to dry, 

 seasoned wood, they penetrate the fibres to a consider- 

 able depth, and a permanent effect is produced. A 

 superficial coat of cold tar will not be found an efficient 

 protection to timber, particularly if it is in contact with 

 moist earth. A single application of hot roofing pitch 

 to a dry, seasoned pine plank, will, however, usually 

 penetrate to about the depth of one inch, as may be 

 seen on examination of a cross section. If both sides of 

 a two-inch plank are thus treated, the wood is practi- 

 cally saturated with the pitch, and its durability will be 

 increased not only by resisting the ordinary elements of 

 decay, but in its wearing qualities when used as a floor.* 

 In building a silo the scantling and boards for sheathing 

 may be cut of proper length, the ends being square, and 

 the hot petroleum or coal tar may then be applied to 



* Mineral pitch and coal tar are refuse products of eras works. A mixture of the 

 two is usually made for roofing purposes, and also for making sidewalks, when it 

 is known as asphalt. Coal tar is too sticky at ordinary temperatures unless it 

 has been boiled, as it should be if used alone, and the pitch, on the other hand, 

 from its higher melting point, is liable to get too hard before it can penetrate the 

 timber, and thus form a superficial coating. By a judicious mixture of the two 

 these extremes are avoided and the mo^t satisfactory results are obtained. In 

 heating or boiling them care should be taken to prevent the inflammable vapors 

 from coming in contact wi h the blaze. Crude petroleum, and coal tar too, may 

 be used by themselves on the scantling and sheathing boards in the process of 

 construction, but on timbers in contact with the ground, and for the inside finish 

 of the walls when the silo is complete, a mixture of the Ur and pitch will give a 

 better body and is therefore to be preferred. A swab, consisting of a suitable 

 stick for a handle about three or four feet long, with a strong cloth wound around 

 one end and stoutly secured with a cord, will be found the most convenient 

 instrument for applying the hot pitch and petroleum. 



