Barbow's Mirror Cruising Compass 



Includes elements to facilitate compassing. 

 Also a simple device, comprising, an indi- 

 cator, a log division, a reading mirror, a pair 

 of sights, and a folding scale. For the pur- 

 poses of determining the number of logs in a 

 tree, and its diameter at the point of mean 

 height, 



First Observation. Pace out 18 paces, or 

 measure 96 feet from the base of the tree. At 

 this point hold up compass box vertically 

 and sight along the upper edge to top of tree, 

 and note the number of 16-feet logs indi- 

 cated in mirror. 



Second Observation. Standing at the same 

 point, sight between the pair of sights, to 

 point of mean height on the tree, at the same 

 time holding knot on cord at the eye (the eye 

 is now equal to 12 inches from the sights.) 

 (having previously opened the folding scale 

 which now rests on partly closed cover.) 

 Carefully sight and continue to close cover until 

 each sight coincides with the width of the 

 tree. This having been done carefully, read 

 the scale which is divided in one hundredths 

 of an inch, to correspond with the width of 

 the tree in inches, when the reading on scale 

 is .40, the tree is 40 inches diameter, if .55, 

 the tree is 55 inches diameter, etc. 



NOTE This scale corresponding with the 

 width of the tree will be found precise enough 

 for all trees containing no more than four 

 logs. 



And all trees above four logs one may trace 

 its diameter by consulting "Tree Scale in 

 Booklet." 



First Example. One finds the tree to 

 contain 5 logs, and the reading of the "Scale" 

 to be .38. See Page 13, find 5 logs line, then 



