24 



Loiidiiu Punilo. which is an imiuire arsenite of lime, is now very seldom 

 used, for the .same reason. As it is a waste iiroiUiet in the maunfacture of 

 aniline il.ves. it is ver.y variable in composition, and therefore unsafe to use. 



(Jrcen Arscnohl. — This is a convenient poison to use. beinj; ijraetically 

 Taris green not crystallised, and is, in some ways, better. Being a very fine 

 powder, it remains in suspeusiou longer and adheres better to foliage. Its 

 chief disadvantage is. it has a rather larger percentage of soluble arsenic, and, 

 unless mixed with fresh lime, as suggested for Paris green, there is danger 

 of it injuring foliage. It may be used in the same proportion as Paris green, 

 viz., one ounce to 10 gallons of water. — Fletcher. 



PuiiiGATioN With HYnEOcy.vNic Acid G.\s. 



During the past few years the method of destroying various insect pests by 

 means of fumigation with hydrocyanic acid gas has been much advocated, and 

 the recommendation has been made in certain of the Board's leaflets. For the 

 destruction of mussel scale, woolly ajihis, mealy bug. thrips, weevils and red 

 siiider in greenhouses, etc., the method is very valuable, while it may also be 

 employed for the fumigation of poultry-houses in case of infestation by lice 

 and mites. 



Xursery stock fumigated with hydrocyanic acid gas before planting will 

 be freed from insect enemies in all stages save that of the egg. 



JI.\TERI.\LS TO BE f SED. 



The materials necessary for purposes of fumigation are: — (1) potassium 

 cyanide of 98 per cent, purity; (2) sulphuric acid of a sijeclfic gravity of not 

 less than 1.83; (3) water; (4) jars and a glass meiisure. 



The following quantities may be taken as a standard for use : — Potassium 

 c.vanide. 1 part; sulphuric acid, li-> parts; and water, 3% parts. 



The proportions of cyanide, sulphuric acid and water to be used, and the 

 amount of space per unit of cyanide, vary slightly as recommended by different 

 authorities, three different \\orkers recommending 1 oz. of cyanide of 98 per 

 cent, purity to every 200, or 300, or 500 cubic feet of space respectively. 



The variation in the amount of cyanide depends to some extent on the 

 character of the i)lants that are being treated, on their strength, whether they 

 are dormant or active, evergreen or deciduous, and also on the .season. lu the 

 case of tender plants, 1 oz. of cyanide may serve for 500 cubic feet of space, 

 while hardy plants may be treated with 1 oz. of cyanide to 200 cubic feet of 

 space. 



Tbeatment of Greenhouses, Conservatories, Nursery Stock, Etc. 



Method of A II lilicat ion. —The glass-house, or other place, which is to be 

 treated, must be received as air-tight as possible. 



The sulphuric acid should be poured very carefully and slowly into the 

 water, which may be put in an earthenware vessel, c.fi.. a large jam-jar. The 

 cyanide of potassium, wrapped in thin blotting i)aper, should then be dropped 

 into the now diluted sulphuric acid. The vessel into which the cyanide is 

 dropi)ed must be so near the door that it can be reached by the outstretched 

 arm of the operator, who should iwimdkitrhi shut the door and close up its 

 chinks by p;iper previously prepared. Another, and better, method is for the 



