203 



In using one part by weight of dry or undissolved potassium cyanide, 

 with one part sulphuric acid and two parts of water. The generator is 

 made of lead and is somewhat in the form of a common water-pail. 

 After the tent is placed over the tree the necessary quantity of the dry 

 cyanide is placed in the generator, the proper quantity of cold water 

 added, and the generator placed under the tent near the trunk of the 

 tree ; the acid is then added to the materials in the generator, a barley 

 sack thrown over the top of the latter, after which the operator with- 

 draws and a quantity of earth is thrown iipoQ the lower edge of the 

 tent where it rests upon the ground to prevent the escape of the gas. 

 After the expiration of fifteen minutes the tent is removed and placed 

 upon another tree. I tested this method on several lemon trees and found 

 that when the proper quantity of material had been used neither the 

 foliage nor fruit on the trees were injured, while neither myself nor sev- 

 eral other persons were able to find a living red scale upon the trees 

 treated in this way. 



The following table, based upon several of the tests referred to above, 

 will aid in determining the proper quantity of each ingredient to use in 

 treating orange and lemon trees : 



It will be noticed that the proportions are I ounce by weight of the 

 cyanide to 1 fluid ounce of the acid, and 2 fluid ounces of water ; or in 

 the proportion of cyanide one, acid one, water two. This being borne 

 in mind, it will be very easy to ascertain how much acid and water to 

 use when once the proper quantity of the cyanide required for treating 

 any given tree has been ascertained. 



In making the tests referred to above, I used commercial sulphuric 

 acid and a medium grade of potassium cyanide, manufactured by 

 Powers and Weightman, of Philadelphia, Pa. It is the same grade of 

 cyanide as that which Mr. O. H. Leefeld purchased at the rate of 44 

 cents a pound, freightage included, as described in my report for 1888, 

 page 125. 



By comparing the table given above with the one given on page 125 

 of my report for the year 1888, it will be noticed that but little more 

 than one-third the quantity of each ingredient is required for a tree of 

 a given size by this new method, as compared with that required by the 

 old one. In the third column of the table given in the previous report, 

 each fluid ounce of the cyanide solution contains half an ounce by 



