AGRICULTURAL EXPERIMENT STATION. 155 



ing, besides, quite an amount of coloring matter. It is quite 

 variable in composition. 



Hammond's Slug Shot does not make a good showing as over 

 nine-tenths (exactly 90.37 per cent) of it appears to be nothing but 

 plaster. It contains only 1.2 per cent of arsenious acid, and 

 approximately 5.00 per cent of a heavy oil. 



Peroxide of Silicates contains only 1.61 per cent of arsenious acid 

 and 84.41 per cent of calcium sulphate. A large part of the calcium 

 sulphate is anhydrous and may have been added either as the mineral 

 Anhydrite or as Plaster of Paris. 



Doyen's Potato-bug Preventive contains 19.09 per cent of arsenious 

 acid and 7.41 per cent of copper oxide. The remainder consists 

 chiefly of starch in large fragments. The presence of copper oxide 

 and the green color of the mixture indicates that the arsenic was 

 added in the form of Paris Green. 



Paris Green contains about forty times as much arsenious acid as 

 Hammond's Slug Shot and the London Purple analyzed over forty- 

 six times as much. Peroxide of Silicates is but little better than 

 Hammond's Slug Shot. A mixture equally as strong as Hammond's 

 Slug Shot can be made by mixing two and three-fourths lbs. of 

 Paris Green with one hundred lbs. of plaster, and a mixture as good 

 as Peroxide of Silicates by mixing three lbs. of Paris Green with 

 one hundred lbs. of plaster. The heavy oil in Hammond's Slug 

 Shot is probably no benefit, as the mixture contains enough 

 arsenious oxide to kill the beetles without it. 



Doyen's Potato-bug Preventive cannot be compared with the 

 others, as the directions require a different method of application. 

 This insecticide is put up in small wooden boxes holding an ounce and 

 a half of what appears to be merely a mixture of about four parts 

 of starch and one part of Paris Green. It is retailed at the modest 

 sum of fifty cents per box. A similar mixture could be prepared 

 from four parts of flour and one part of Paris Green, at a cost 

 of less than one cent per box. Flour, which is cheaper than starch 

 and just as good, has long been used as a carrier for Paris Green. 

 The novelty of this insecticide is the method of application as 

 shown by the following directions pasted on each box : 



