ESTIMATING GAS FOR ORCHARD WORK 77 



cated, it is difficult to measure and determine accurately 

 the cubic content of a tented tree. To simplify the 

 measurement and estimation of the tent the following 

 table has been prepared by Prof. Woodworth, of Cali- 

 fornia. The center column gives the various doses 

 corresponding to the size of the trees in the columns 

 on either side. Thus, on one side it has been calcu- 

 lated so as to give three parts of hydrocyanic acid gas 

 in 1000 parts of air ; on the other side, two parts in 

 1000 of air. For winter treatment for deciduous trees 

 the first or 0.3 per cent, gas is suggested. This is 

 about equivalent to the general recommendations given 

 for the Eastern States. One-half of this amount is not 

 far from the commonest practice in California for 

 citrus trees. The 0.2 per cent, formula is suggested 

 for citrus trees. It agrees with the amounts used by 

 some of the most successful fumigators in California. 

 Other individuals get fair results with scarcely more 

 than half this amount. 



The measurements to be taken when using this 

 table are (i) around the tent, and (2) from the 

 tent from ground to ground. If these two measure- 

 ments are about equal, as will be found on many 

 orange trees, the number nearest the measure- 

 ment is found in the circumference column, and 

 the corresponding dose will be seen in the center 

 column. If these two measurements are not nearly 

 the same, the outside columns become useful, for 

 they show for each size how much difference must 

 occur to make necessary a half ounce increased or de- 

 creased in dose ; that is. for each differential there must 

 be added or deducted one-half ounce of cyanide. For 



