WINTER BIOTH; LONDON PURPLE. 175 



Mr. F. Nixon, of Great Eversclen, near Cambridge, who i? 

 well qualified to form an opinion on the subject ; these will bt 

 found at pp. 107, 108, preceding. 



It is to be remembered that, like Paris-green, it is a Poison, 

 and must be used with care accordingly. 



In the case of either of these arsenites, the strength of the 

 mixture should be tested by apj^lication on a small scale, 

 before use generally, so as to avoid risk of broadscale damage. 

 But the following observations by Prof. John B. Smith, from 

 his entomological work* referred to below, may be of service : — 



" Both the insecticides just mentioned can be made entirely 

 harmless to foliage by adding weight for weight of caustic 

 lime when mixing ; that is to say, in preparing the poison for 

 use take one pound of Paris-green or London-purple and one 

 pound of quicklime ; add water enough to slake the lime, and 

 mix thoroughly while hot, so as to incorporate lime and poison 

 completely. This will fix with the lime every particle of the 

 soluble arsenic contained in the mixture, and it can then be 

 diluted with water and applied at almost any reasonable 

 strength, without much danger of injury to even the most 

 tender foliage." — (J. B. S.) 



An arsenite of lead, known as "gypsine," has much more 

 recently come into use in America with much the same range 

 of usefulness as the two oUier ■poisons mentioned above; but 

 as yet I am not aware of it having been adopted for service 

 here. 



Kcrosine emulsion. — For those who object to the use of 

 poisons, the application of " kerosine emulsion " ranks next 

 after that of Paris-green as an insecticide for broadscale use 

 on leafage of orchard trees to make a general clearing of 

 caterpillars. 



In the course of the preceding pages recipes have been 

 given for preparation of this "emulsion," and of various 

 other soft-soap and mineral oil mixtures very similar in com- 

 position, for reference to which see Index ; but it should 

 always be remembered that unless the operators are thoroughly 

 well informed of their work, that it is only prudent to experi- 

 ment before beginning broadscale application as to the effects 

 on leafage of the strength that is being employed. 



In regard to spraying machines, the call for them has been 

 followed by such a plentiful supply, that to particularize one 

 kind rather than another might be deemed undesirable ; but 

 at least it may be admissible to point out the serviceableness 

 of "the knapsack sprayer," which is a can or reservoir that 



* 'Economic Entomology,' by John B. Smith, Sc.D., Entomologist to the 

 New Jersey Ag. Coll. Exp. Station, &c., p. 435. Philadelphia, U.S.A. : J. B. 

 Lippincott Co. 1896. 



