78 



The rings are slipped onto the tops of two poles, from 16 to 20 

 feet long, the butts of which are placed on each side of the tree 

 to be covered. Two ropes, the length of the poles, or longer, 

 are attached to their tops; the other end of each rope is held by a 

 man with his foot on the butt of the pole ; the men pull their 

 ropes, the tops of the poles rise bearing the front edge of the 

 tent, which is carried over the tree and the length of the pole 

 beyond it, thus covering the tree. A tape measure is passed around 

 the covered tree, giving its circumference ; the marks on the canvas 

 show the distance over the top, and from a prepared table or sched- 



Dosage Schedule No. A, for sodium cyanid. (U. S. Dept. of Agriculture.) 



ule of dosage, the operator can see at a glance just how r much 

 cyanide to use for each tree thus measured. This is the latest 

 improved system known as the Woglum System. 



The "dose" of sulphuric acid is diluted with water and placed 

 in a deep earthen pot, placed under the tent by raising one side, 

 the cyanide is dropped into it, the tent closed quickly, and left 

 on the tree one hour. 



The Dose The chemicals used are either cyanide of potassium 

 or cyanide of sodium (the latter usually now as it is cheaper and 

 gives the best of results) from which the gas is liberated by emers- 



