258 



resin wash is that the nozzle frequently becomes clogged, but Mr. 

 Coquillett found that this could be almost entirely prevented by 

 first straining the solution through a piece of thin tarlatan cloth. 



Another remedy now much used in California against the 

 red scale ( Asjndiotus aiirautii), is hydrocyanic acid gas. Professor 

 R^ley thus describes the process : — " The cyanide is dissolved by 

 boiling in water for a few minutes, using 1 gallon of water for 

 each 5 pounds of cyanide. To generate the gas, sulphuric acid is 

 caused to flow upon the cyanide solution in a fine stream, causing 

 the gas to be rapidly given off" in the form of a whitish fog. The 

 moisture is taken up by passing the gas through sulphuric acid, 

 which by reason of water taken up becomes diluted, but may still 

 be employed to generate fresh quantities of gas." 



" The gas is confined to the trees under treatment by means 

 of a suitable canvas tent or fumigator, of which a number of 

 styles have been patented. They are constructed so as to be 

 lowei'ed over the tree from above or to inclose it from the sides." 

 It is found that the gas must be dried as above described, as 

 otherwise it is injurious to the foliage of the trees. It is also stated 

 by Mr. Coquillett that the trees are less liable to injury when 

 fumigated at night, than when treated in the day-time. The ap- 

 paratus has lately been simplified, so that it is possible for a 

 planter to fumigate his orchard at the rate of 30 to 40 trees a 

 night. The ordinary commercial fused potassium cyanide is used 

 in the manufacture of the gas, which, it must be remembered, is 

 highly poisonous. 



(To be Continued.) 



