726 



AMERICAN FORESTRY 



No.l. — Large cavity in an 

 Elm filled with cement 

 blocks with layers of tarred 

 paper between. 



No. 3. — Cavity shown in No. 

 2 which has been nailed and 

 partly filled with cement 

 and showing placing of rods 

 and use of wire dam. 



No. 2. — Excavated cavity ready 

 for treating and filling. 



No. 4. — A later stage of the work 

 showing in No. 2. 



No. 5. — The same cavity after fill- 

 ing is completed. 



Pl.xte No. 5. — Cement Cavity Fillinss, Showing Different Types .\ni> Successive St.\ges. 



18 to '■ii inches. ( )flentiine.s a single 

 bolt can be placed so as to support bo;h 

 sides (Plate No. 4, figure 2). In cer- 

 tain cavities it may be necessary to 

 place bolts at different angles (Plate 

 No. 4, figure 3). In any case a strip 

 of uninjured cambium at least an incli 

 wide should be left between the edge 

 of the cavity and the l)(jlt. ( )n medium- 

 sized trunks, after deciding where the 

 bolts can most efficiently be placed, a 

 very sharp half-inch bit, sufficiently 

 long to reach through the trunk and 



ca\'ity, can Ijc used to bore the hole for 

 the bolt. On large, heavy trunks a 

 larger bit should be used. Heavy oval 

 or round iron or steel washers, about 

 three times the diameter of the bolt, 

 should be countersunk into the wood 

 by carefully cutting away the bark at 

 both ends of the hole with a sharo 

 gouge or chisel (Plate No. 4, figures '2, 

 o and 4). 



All split cavities must be securely 

 l)olted, particularly near the upper jxirt 

 If the split comes from a crotch., all 



