32 THE HOP APHIS IN THE PACIFIC REGIOX. 



should supply at least two lines of hose at 120 to 150 pounds pressure, 

 and should be in such order that there will be few breakdowns or 

 delays. Good work can be done with the hand pumps (see PL VII, 

 fig. 1), the gasoline power outfits (PL VIII, figs. 1, 2), the compressed- 

 air sprayers, etc., provided they meet these requirements and are 

 supplemented by an efficient mixing and supply system. 



The knapsack spraying machine (PL VII, fig. 2) may, under some 

 circumstances, be of value for work on a very small scale, but is not 

 at all practical in a commercial hopyard. 



BOILIXG AXD MIXING PLAXT. 



In designing a boiling and mixing plant for work on a large scale it 

 is very desirable to arrange the tanks so that their filling and empty- 

 ing is accomplished by gravity. 



The uppermost tanks should be used for steeping the materials and 

 should be supplied with water from a hydrant; the lower ones 

 should be filled by drawing from the upper ones, or, when diluting is 

 necessary, from a hydrant. The lower tanks, however, should be 

 high enough to drain into a supply wagon. 



DESCRIPTION OF TANKS. 



The boiling and mixing tanks at Independence, Oreg., were made 

 of No. 18 galvanized iron, riveted and soldered together, a f-inch 

 iron pipe forming a brace for the tops. Three braces of ^-inch angle 

 iron, placed 3 feet 4 inches apart and riveted to the sides of the tanks, 

 together with a framework of 2 by 4 planks, prevented the tanks 



from bulging 



ARRANGEMENT OF TANKS. 



The arrangement of tanks shown in Plate VI, figure 2, was found 

 very satisfactory. Two boning tanks 10 by 3 by 3 feet 9 inches, 

 heated by steam, were placed upon a 10 by 12 platform, elevated 10 

 feet from the ground. Passageways were left between and around 

 the tanks. On a near-by but lower platform were three 375-gallon 

 tanks for mixing and storage. A swinging outlet pipe drained the 

 boiling: tanks and directed the materials into anv one of the three 

 tanks. From the lower tanks the material was run through a long 

 hose into the supply wagons. In order thoroughly to strain the 

 materials the entrances of all the outlet pipes were screened with 

 wire gauze anc ^ tne ends of the hose were covered with cheesecloth. 



FIELD OPERATIOXS. 



SUPPLY WAGONS. 



When extensive spraying operations are being carried on it is 

 essential to have an adequate supply system. In an emergency a 

 farm wagon containing barrels of spray (PL VIII, fig. 2) can be used, 



