136 



pend upon the preparation of the mixture, great care should be taken 

 to accurately follow the directions. The formula in general use is: — 



ioap ... ... ... -Jib 



Kerosene ... ... ... 2 gals. 



Soft water ... ... ... 1 gal. 



4 Dissolve the soap in the water heated to boiling, then add the 

 kerosene (to the hot mixture), and churn it until a creamy fluid re- 

 sults, which thickens on cooling, and adheres to glass without separating 

 into oily particles.' 



Whale-oil soaps are preferable, but any kind may be used. I have 

 personally made a very successful emulsion, employing the common 

 country soap, which seems to be particularly well adapted to retaining 

 the oil in an intimate mixture, and which, in this combination loses its 

 own objectionable properties. The most important part of the process 

 is the churning. This must be most thoroughly carried out. It can be 

 satisfactorily managed by repeatedly drawing up and expelling the 

 mixture through an ordinary garden syringe or a force pump. A more 

 lengthy method is to stir the mixture vigorously with a whisk of twigs. 

 The liquid should be boiling hot during emulsification, and then, if kept 

 in a cool place, it is said to last for a year or more without separating. 

 If insufficiently churned, the mixture will afterwards become separated 

 and the oil collect at the top. A properly compounded emulsion will 

 mix with w r ater in any proportions. 



For use against scale insects a strength of one part emulsion to 

 ten of water is found to be effective. As in all preparations of which 

 petroleum is an ingredient, it can be more safely used on cloudy days. 

 When used in hot sunshine, it is liable to burn the foliage and injure 

 the tender shoots of the plant, but the danger of injuring is much less 

 with a properly prepared emulsion than with mechanical mixtures of 

 kerosene and w r ater. Mr. Marlatt, in some ' Notes on Insecticides,' * 

 gives the following particulars of experiments which show that kerosene 

 emulsion can be used of considerable strength without causing apprecia- 

 ble injury to the plants. But it cannot be recommended for general use 

 at a greater strength than mentioned above. Mr. Marlatt writes : ' About 

 the 1st May, when the foliage was in the vigour of its early growth, a 

 number of plants-peach, Japan quince, elm, pine, and strawberry-were 

 treated with the following strengths of kerosene and whale-oil soap 

 emulsions, made after the standard formula : Diluted (1) with 

 8 parts of water, (2) 4 parts of water, (3) 9 parts of water, and 

 (4) 14 parts of water, or the emulsion at J, J, y^, and strength. The 

 application was very thorough, and the limbs and tiwgs were thorough- 

 ly wetted by immersion in the insecticide. The treatment was made on 

 a very bright, warm day, in the early afternoon. No rain occurred for 

 four days, after which there were heavy rains. No injury whatever 

 developed in the case of the pine, strawberry, and elm with any of the 

 strengths used. With peach the injury was trifling, a very small per- 

 centage, perhaps one or two per cent, of the leaves turned yellow and 

 fell to the ground, but I am inclined to believe that this was merely the 



* Insect Life, Vol. VII., p. 116. 



