14. _Soap._ Undoubtedly a valuable remedy, and perhaps, in some cases, as efficient as kerosene; _but it does not destroy the eggs_. A solution of 3/4lb. of soap to a gallon of water, _applied hot_, was entirely successful in California: three months after its application no living scale-insect could be found (Comstock). The time of the year is not stated. In another case the solution was applied cold: "four days after no living insect could be found;" but, again, the time of the year is not stated, and no mention is made of the eggs. Still, a strong solution of soap may be said to be one of the best remedies against the larvæ and adult insects--proportions from 1/4lb. to 1/3lb. soap to one gallon of water (Comstock; Hubbard; Personal experiment). 15. _Soda, caustic._ Strongly recommended by many persons. It injures the tree, _and does not kill the eggs_--two things which are decidedly against its use. Gardeners may have been led to employ it from finding that in some instances it clears away the black fungus-growths (Chap. III.), and imagining this to be a clearance also of the scales. 16. _Soda, silicate._ Kills some insects, _but no eggs_, and injures the tree (Hubbard). 17. _Sulphate of iron._ "A common ingredient in patent remedies;" most injurious to vegetation. It does not affect scale-insects (Hubbard). 18. _Sulphur._ Another substance, the object of a kind of superstitious veneration amongst gardeners. It is excellent against fungoid growth, but of little value against scale-insects. Here, again, the clearing of the black fungus has probably been taken to mean also the destruction of the insects (Hubbard; Comstock; Personal experiment). Comstock says that in America people often bore holes in their trees and stuff them with sulphur, under the notion that the substance will be taken up by the sap, and poison the insects: quite a futile idea. 19. _Sulphur and lime._ A dangerous compound, and useless unless applied in such strength as to kill the tree. Its fumes are poisonous, and it may seriously injure the face and hands (Hubbard). 20. _Sulphur and snuff._ Equal parts mixed and dusted over _Lecanium hesperidum_ on a wet day were quite successful (Comstock). But the mixture would be too expensive except for conservatory plants, and doubtless the snuff alone would be quite as efficacious. 21. _Sulphuric acid._ "Killed nearly all the scale-insects, and very nearly killed the tree" (Hubbard). No mention is made of its action on the eggs. 22. _Soot._ Useless (Hubbard; Comstock; Personal experiment).