PRACTICAL TREE SURGERY ' 391 



(Fig. 306 B). The heads of the nails finally are completely embedded 

 in the cement (Fig, 306 E). If the cavity is already bolted, it may not 

 be necessary to use many nails, because the bolts help to hold the 

 cement in place. 



298. Treating. — After the decayed and diseased matter has been 

 completely excavated and the edges of the sap wood and bark shel- 

 lacked, the ne.xt step is to sterilize the interior of the cavity in order 

 that all germs of <lisease or decay may be killed and that any v.-hich 

 may come in contact with the cut surfaces during subsequent opera- 

 tions may be destroyed. Creosote appears to be one of the best 

 preparations to use. Every cut part of wood and bark must be 

 creosoted. Over this a heavy coating of tar or hot asphalt should be 

 applied before the cavity is filled. 



299. Mixing the cement.— .'\ good grade of Portland ceinent and 

 clean, sharp sand free from loam (1 part of cement to 3 or less of 

 sand) should be used. The mixing may be done in a mortar bin, ; 

 wheelbarrow, a pail, or in any other available receptacle sufficiently 

 large. A quantity of dry cement and sand sufficient to fill the cavitv 

 should be thoroughly mixed before the requisite amount of water to 

 make a rather stiff mortar is added, and the whole mixture worked 

 to an even consistency. In large cavities fine gravel, free from loam, 

 is sometimes substituted for the sand. 



300. Cementing. — For placing the mixture in the cavity a mason's 

 flat trowel and an ordinary garden trowel with a curved blade will 

 be found convenient. A tamping stick, 1 or 3 inches thick and 1 

 to 3 feet long, according to the size of the cavity, will be needed. 



A layer of cement 2 or 3 inches deep may now be placed in the 

 bottom of the cavity with the garden trowel and tamped firmly in 

 place. This operation is repeated until the cement is S to 12 inches 

 thick. Wet rocks of various sizes may be embedded in the cement 

 provided they do not reach within an inch or two of its outer face. 

 If the mi.xture is too wet, it will tend to run out of the cavity unrler 

 the operation of tamping. If too little water has been used, it will 

 not pack down promptly. 



The top of the 8 to 12-inch block of cement is smoothed with the 

 flat trowel so it will slant slightly downward from back to front, 

 in order to facilitate drainage. Over the top of this cement block 

 a double or a single sheet of tarred roofing (or thinner) paper is 

 placed after it has been cut so as to fit the cavity. On top of this 

 another block of cement is built as soon as the first block is suffi- 

 ciently hard to stand the weight and tamping without forcing any 

 of it out at the bottom of the cavity. 



If the interior of the cavity extends well above the level of the 

 external opening, it may occasionally be necessary to bore or cut 

 a downward slanting hole from the outside to the top of the interior 

 cavity, through which a watery mixture of cement may be poured to 

 fill the upper part of the cavity and the hole. The main opening 

 of the cavity must be completely closed with the stift'er cement be- 

 fore this watery mixture is introduced. 



