MATERIALS 53 



with water, and the best way of proceeding is to incor- 

 porate it first with a little hot water in a mortar, etc., 

 and then to add the rest of the water to it. The propor- 

 tions recommended vary very largely, from 2 ozs. up 

 to 10 lbs. to every 10 gallons of water, though such a 

 high proportion as the latter, would seem to be very 

 excessive. 



20. Sulphur aud lime. — A mixture of sulphur and 

 lime is to be preferred to sulphur only, as being 

 probably more efficacious. Even when the two are 

 not boiled together, a certain amount of combination 

 occurs, calcium sulphide and other compounds being 

 formed. The substances may be used in the dry 

 condition, and dusted on to the trees, preferably when 

 these are wet with dew or mist. Either equal weights 

 of flowers of sulphur and ground quicklime, or two 

 parts of sulphur to one of lime, are recommended. 

 Some scorching of the foliage often occurs ; this is 

 reduced by using dry, freshly slaked lime, instead of 

 quicklime, but the insecticidal value of the mixture 

 is likely to be somewhat reduced in that case. 



21. Sulphide of calcium. — When lime and sulphur 

 are boiled with water for some time they combine to 

 form a mixture containing various sulphides of 

 calcium, which is useful for the treatment of surface 

 mildews. It is hardly worth while, however, to make 

 this sulphide, as it can be bought at a low price in 

 the form of a 40 per cent, solution, and one part of 

 this in 100 of water is sufficiently strong for applica- 

 tion : moreover, the sulphide of potassium appears to 

 be generally preferable to that of calcium. 



22. Liuie-sulphur-salt wash {California wash). — This 



