EXTERIOR DEFECTS 



113 





downwards. The form which it takes depends upon the species of 

 fungus, and of trees attacked. The unsound portion is surrounded by 

 a stained portion which is yet sound. The area of the rot increases 

 with age of tree and time elapsing since the infection took place. 



In deducting for rot, the amount of the loss depends upon the location 

 of the point of infection, usually a rotten knot. Stain which shows at 

 one end of a log requires no deduction if the rot of which it is an evidence 

 lies in the adjoining log as cut from the bole. On the other hand, two 

 or more rotten knots in a log, with stain showing, means a heavy dis- 

 count and a possible cull. Sawyers are accustomed to leave such logs 

 in the woods and even in the tree without sawing them. Rot from a 

 single point of infection will extend 

 from 2 feet to as much as 10 or 1.5 

 feet in either direction. It is deepest 

 and most complete at the point of entry, 

 tapering out with increasing distance 

 from this point. Rot of this character 

 is so irregular that experience is re- 

 quired in observing such logs sawed 

 before proper deductions can be made 

 by scalers. 



In deducting for interior rot, the 

 probable extent and shape of the un- 

 sound portion therefore depends upon 

 the appearance of the ends taken in 

 connection with unschund knots. The 

 only portions of the log which can be 

 scaled are those which will produce 

 sound boards having the minimum 



length and width prescribed in the rules for scaling. The deduction 

 will take the form of a per cent of the sound scale. Diagrams are some- 

 times of assistance, but in logs containing rotten knots the extent of 

 rot is usually greater than revealed at the cross section. The appa- 

 rent cull must ordinarily be increased, from 25 to 100 per cent. 

 Since deduction of length is equivalent to a percentage reduction of 

 scale, this method is frequently used. 



Peck in cypress, and the rot found in Incense cedar gives no 

 external indications, and is not always revealed on the cut ends of logs. 

 This condition tends to the substitution of a straight percentage deduc- 

 tion from the total scale instead of reducing the scale of individual 

 logs for defects. 



92. Exterior Defects. Exterior defects, on the sides of logs, include 

 unsound sap, surface checks, cat faces, fire scars, and scars caused by 



Fig. 19. — Log A is infected at 

 the point X and is a cull. At 

 the lower end no rot shows, 

 but stain only. This stain 

 therefore shows at the upper 

 end of log B, but causes no 

 deduction for cull. 



