Cyanide Gas Remedy p^or Scale Insects. 



447 



the latter method of judging' the size is now recommended. The present 

 dosage table may be used M'ith either method. The distance around 

 should be measured by a tape line, or by carefully checked pacing, and 

 the distance over by the aid of marks painted on the covers. The 

 marking had best be done along two seams, about six feet apart, across 

 the middle part of the cover, the distance in feat outward from the 

 middle being indicated by bold figures. When a marked sheet covers the 

 tree, the distance over the top can be told voy closely by noting the 

 tigures and where they are. For example : if one of the lines of 



Fig. 10. — Sheet Cover and Derrick Polen.—At left, sketch td show liftiiiii: of :i sheet with 

 derrick poles. Commonly it is uecessarj' f(.)r the ^uy lope men to stand in 

 front of and with their feet on the base of the poles to keep these from slipping 

 forward. At right, sketch to show construction of derrick jjole. The small sketch 

 in the middle shows the simplest tackle fittings for a derrick pole ; the pulley 

 blocks are such ;is are regularly stocked by ship chandlers, etc. The small 

 sketch at right shows a "catch place," a gathering of tlie sheet enclosing a 

 soft ball to give size with a ring into wJiich the pulley hook or top of changing 

 pole is inserted ; the sole object of the second ring is to jingle when the sheet 

 is moved and thus help to locate the catch place in the dark. 



figures i 

 is at the 

 level on 

 ;:I2 feet, 

 easy to 

 figures. 



s directly over the highest i)art and the figure 15 (U) this line 



ground-level on one side while the figure IT is on the ground- 



the other side, it is evident that the measurement wanted is 



If the highest point lies between the two lines, it will be 



judge what sho\ild be added to the distance shown by the 



/Proportions of the ( 'lie in i cols. — The proportions of the chemicals 

 for a charge should be : — 



Sodium cyanide (12G-130 per cent.) 1 oz. by weight. 



Sulphuric acid (94 per cent, or higher) ... 1^ oz. by measure. 



Water 2 oz. by measure. 



The water should be put in the generating vessel, next the acid, 

 and then before the mixture cools the cyanitle dropped in, the dish 

 covered, and the cloth dropped. Great care should be taken not to 

 touch the cloth with acid or with a hand that has come in the least 



