362 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 12 



A critical examination of the schedule shows certain outstanding 

 features. SmaU trees are dosed almost in proportion to cubical con- 

 tents, larger sized trees approximate the ratio of surface area of a 

 domed-shaped figure to its cubical contents. The tendency is for tall 

 trees to receive a heavier dosage than low trees ha%ing the same 

 cubical contents. 



Each unit of dosage in this schedule is based on a delivery of 18 

 cubic centimeters of liquid hydrocyanic acid, 95 to 98 per cent pure, 

 in the form of a very fine spray beneath the tented tree. Thus a tree 

 30 feet over by 40 feet around calls for 10 charges of 18 cubic centi- 

 meters (180 cubic centimeters). By graduating the machines used in 

 generating the gas in numbers corresponding to those on the schedule 

 and providing that each graduation dehvers a charge equal to the 

 number of cubic centimeters of which itself and 18 are the product, 

 this schedule is made equally practical to former schedules. 



This dosage schedule is based on the same dimensions of tented 

 trees as was the original Schedule I for pot-fumigation, i. e., the dis- 

 tance around the tented tree and the distance over the middle from 

 ground to ground. The correct dosage for any tree is found in the 

 square formed by the intersection of the fines running from the two 

 numbers representing these measurements. It is expected to give 

 results equivalent to Schedule I for potassium or Schedule I for sodium 

 cj'^anid and should be substituted for these schedules wherever for- 

 merh' employed in pot- or machine-generation. 



At a temperature of 40° F., the superiority of Hquid hydrocyanic 

 acid to pot-generated gas is not so marked as at higher temperatures 

 of fumigation. Therefore, it will be necessar}- in fumigation at such 

 low temperatures to increase the dosage over that used during warm 

 weather. 



A three-quarter or 75 per cent schedule was originally prepared by 

 the writer for pot work and many others, such as 65, 85, 110, 120 and 

 125 per cent schedules have been calculated by others. The necessity 

 of such a large number of schedules is questionable. Furthermore, 

 the original identity of these schedules is frequently lost by field use 

 and thereby sometimes becomes a source of confusion to the fumigator. 

 The preferable method, and the one advocated at this time by the 

 writer, is to have differently graduated attachments which are easily 

 and quickh' adjustable to Hquid "gas" machines when different sched- 

 ules are required. These will insure uniformity for all dosages and 

 require only one dosage chart for aU fumigation. Such attachments 

 graduated on the unit dehvery basis of 14 cubic centimeters, 16 cubic 

 centimeters and 20 cubic centimeters, when used with the new dosage 

 chart, will produce the equivalent of 78, 89 and 111 per cent schedules, 



