INTERIOR DEFECTS 111 



or if the volume of the rotten core, ' ' shows a smaller cull than the 



15 



sound scale of that part of the log, deduction by diagram of the squared 



core is made (preferably by Tiemann's formula) to a length judged to 



include the rotten portion. 



Example. A log 12 feet long and 20 inches in diameter at top end has a rotten 

 butt 6 feet long, the rotten core measuring 17 inches across. Although the butt 

 measures 25 inches, leaving a 4-inch rim of sound wood, the inscribed circle repre- 

 senting the top of the log is only 20 inches, and the butt is a cull. This observation 

 is borne out by applying Tiemann's formula: 



Scale of 12-foot log, 210 board feet, 

 Scale of 6-foot length, 105 board feet, 

 Cull for butt rot, f (18 2 )^ = 108 board feet, 



or more than the sound scale of butt. This deduction is not applied to the whole 

 log but only to the butt. 



The scale of the log is then 105 board feet on the basis that the upper half is 

 sound. 



If this core should measure 13 inches, 



Cull for butt rot f (14 2 ) 1 ^-=65 board feet. 



The scale of the log is then 210—65 = 145 board feet. 



But if the minimum board length should be over 6 feet, the first log will be 

 culled entirely, and from the second log, a cull of §(14 2 )-j-§- or 131 board feet 

 Scribner Decimal C is deducted, leaving a scale of but 79 board feet, or 37.6 per 

 cent of the merchantable contents. 



Shake. Shake is a mechanical defect caused by wind. The annual 

 rings have separated at one or more points, giving a circular or ring crack, 

 and the board falls to pieces when sawed. This flaw is found at the butts 

 of such species as hemlock, and is seldom more than a few feet in length 

 although entire logs may be shaky. Lumber sawed from shaky por- 

 tions of logs is often worthless. 



A single circular shake is scaled out in the same manner as butt rot 

 except that the contents of a smaller sound core lying within the shake 

 may be added or restored to the scale. The diameter of this interior 

 core should be measured at the small end of the culled section if it extends 

 through the log, while the diameter of the culled portion is measured 

 at the butt or large end. In short sections whose length is guessed at, 

 a proportionate reduction from butt diameter is made in scaling the 

 sound core. This same method is used to scale out pitch rings, where 

 this is deemed necessary. In most cases pitch is considered a sound 

 defect (§ 82). Where shake shows in several rings, the entire shaky 

 portion of the log is butted, by shortening its length. 



