CYANIDING. 



51 



a long time. Keep the houses shut for forty minutes, and 

 keep the punkahs swinging for thirty minutes to distri- 

 bute the gas thoroughly. At the expiration of the time 

 throw open all doors and later the ventilators, to allow the 

 fumes to escape before anyone is allowed to work in the 

 houses. If this mild dose is found insufficient to kill the 

 insects on the plants, increase the dose Joz. at a time, 

 with the corresponding quantity of acid, until the right 

 strength is found. 



" The Apparatus. — Anyone wishing to do cyaniding 

 on a larger scale cannot do better than make himself the 

 following apparatus, the invention of Mr. Gr. F. Strawson. 

 One set of apparatus is required for every 2,000 cubic feet 

 of air space to be cyanided. The illustration given here- 

 with shows a complete set of apparatus ready to be set in 



APPARATUS FOR CYANIDING. 



action. The punkah, P, is made of pieces of board nailed 

 to cross battens, and is hung by strings from its top corners 



