20 



below oue-half tlie proportions of kerosene become uncertain. If spray- 

 ing be suspended, as would naturally result in passing from one tree or 

 plant to another, and the oil stopcock be not closed, there is a very con- 

 siderable increase in the percentage of oil, api)arently from a passage of 

 the oil into the pump and water tank in spite of the presence of the oil 

 valve. It is therefore necessary to immediately shut off the oil after 

 every spraying. Even this will not prevent a variation in the results, 

 because the first minute's spraying, even with this precaution, will 

 show a greater percentage of oil than subsequent pumping will produce. 

 This seems to be due to the accumulation of oil in the air chamber of 

 the pumj) as a result of the action of the latter, as explained by Mr. Goff. 

 There is also a separation of the oil and the water held in the length of 

 the spray tube. 



Even when spraying steadily, without intermission, more or less oil 

 escapes from the oil tank through the pump into the water tank. This 

 is probably by means of the drawing of the oil into the air chamber of 

 the pump owing to the faulty position of the former, as pointed out by 

 Mr. Goff'. The series of experiments tried, listed in the accomx^any- 

 iiig table, indicate the different results obtained by varying the con- 

 ditions of spraying, all of which would frequently occur in actual prac- 

 tice. They show a range for the two-tenths gauge mark which should 

 l>roduce 20 per cent oil, of from 10 per cent to 23 per cent oil. Spray- 

 ing continuously, without any stop or shutting oft' of the oil, will i)retty 

 regularly secure 10 j)er cent oil at the 20 per cent mark on the gauge 

 if the two tanks are half or more than half full. If a stop of a minute 

 be taken and the oil immediately shut off' the first spray following has 

 an av^erage of 13 ^er cent oil. If the oil stopcock be not turned off', but 

 left at the gauge mark, as directed in the bulletin referred to, and 

 which would naturally be done in passing from one tree to another, the 

 percentage of kerosene in the first minute's spray will range from 1(5 to 

 23 per cent, and thereafter 10 per cent. Finally, spraying at the differ- 

 ent percentages indicated on the gauge, one after another, taking the 

 precaution to operate the machine after each change for a sufficient 

 time to produce the normal mixture, the different amounts of oil ]}yo- 

 duced do not agree with the gauge indications, except the highest — 10 

 and 50 per cent. At the most serviceable percentages — i. e., 10 and 20 

 per cent — the amount obtained was about one-half that indicated by the 

 gauge. 



It was found by rei)eated experiment that when the index indicated 

 20 per cent oil, uniform pumi:)ing yielded pretty regularly, under favor- 

 able conditions of tanks, about 10 per cent strength of oil. This is 

 equivalent to a dilution of ordinary kerosene emulsion with 5| i^arts 

 water. A number of plants, including peach, pear, cotton, mulberry, 

 and tomato, were sprayed at this strength. With the exception of the 

 mulberry, no injury to the foliage resulted. With tbe mulberr}^, how- 

 ever, a considerable spotting of the leaves with yellow followed in a day 

 or two. 



J 



