84 The Spraying of Plants. 



increase the amount of oil in the emulsion. I now use 66 per cent 

 emulsion diluted 1 to 9, and these, although sufficiently strong 

 for long scale, are not sufficiently penetrating to kill the eggs of 

 purple scale. . . . The following are my estimates for a stan- 

 dard wash of whale-oil soap and kerosene, emulsion 66 per cent 

 oil, diluted to 1 to 9 (one gallon emulsion = 10 gallons wash) : 

 whale-oil soap, pound ; water, 1 gallon ; kerosene, 2 gallons." 



In the annual report of the Commissioner of Agriculture for 

 1884 a formula is published which contains twice as much 

 soap as Hubbard's original one, the other ingredients remaining 

 the same. This has become most commonly known under the 

 name of the Riley-Hubbard formula for the kerosene emulsion, 

 and is used to-day unchanged. It is prepared as follows : 



" Kerosene, 2 gallons ; common soap, pound ; water, 1 gallon. 



"Heat the mixture of soap and water and add it boiling hot 

 to the kerosene. Churn the mixture by means of a force pump 

 and spray nozzle for five to ten minutes. The emulsion, if perfect, 

 forms a cream, which thickens on cooling, and adheres without 

 oiliness to the surface of the glass. Dilute with cold water 

 before using, to the extent which experience will indicate is 

 best." 



The scale insects found upon the orange trees in California 

 may be cited as further examples showing that obstacles can be 

 overcome if only sufficient attention is directed towards them. 

 These insects were a serious pest on the Pacific coast, and they 

 are not entirely under control even at the present day, but their 

 great numbers in former years aroused the fruit growers to ener- 

 getic measures. Many compounds were recommended for the 

 treatment of the pests. The preparations were generally in liquid 

 form, and may be considered as rather elaborate outgrowths of 

 compounds whose value had long been known. The following 

 are good examples of these remedies, whose number was almost 

 endless : l 



1. Forty-six pounds whale-oil soap, 4 gallons coal oil, 100 

 gallons water. 



2. Twenty-five pounds brown soap, 6 pounds wood potash, 4 

 gallons coal oil, 100 gallons water. 



1 Ellwood Cooper, "California Fruit Culture," a report of the fifth annual con- 

 vention of California fruit growers. 



