xxii Remedial Measures and Insecticides. 



to be treated, a more powerful apparatus may be mounted on a 

 cart, and drawn by horse or bullock power. In such cases two or 

 more lines of hose and nozzles can be worked from the same tank. 



II. Strength. — The materials employed in the construction 

 of the machine should be such as are not readily corroded by the 

 mixtures used. Mr. Lounsbury, in his report for the year 1896,* 

 gives the following very practical hints on this subject : — 



* Iron is so quickly corroded by many of the common insecti- 

 cides and fungicides that pumps in which the working parts are of 

 this metal are not desirable. These parts of the pumps should 

 always be made of hard brass. For the sake of economy, the 

 bodies of most pumps are made of iron, but even here the use of 

 brass lends greater durability, and is an advantage which in the 

 end will probably pay for the additional initial cost. Rod-like 

 parts and thin handles of cast iron are objectionable because so 

 easily fractured. Any parts of rubber are damaged by contact 

 with paraffin. Ignorance of this fact has led to the ruin of a large 

 number of Vermorel knapsack pumps, in which a circular rubber 

 disc is used for the propulsion of the liquid. The paraffin causes 

 the rubber to swell, and thus become useless for its purpose. 



'Copper is the best metal for tanks in knapsack pumps, and 

 attention should be paid to the thickness of this metal. Thin 

 copper will rapidly wear through. Tanks of sheet iron or tin are 

 soon ruined by contact with liquids containing copper compounds, 

 such as Bordeaux mixture and Paris green, and these preparations 

 are also injuriously affected. But even copper tanks are not 

 suitable for use with all spraying mixtures, since this metal is 

 acted upon by the sulphur in such compounds as " eau grison " and 

 lime- sulphur-salt mixture. In these cases, the sulphur leaves the 

 lime, with which it had united during the process of cooking, and 

 unites with the copper to form copper sulphide. This compound 

 forms in a thin black layer over the copper, which, if it would 

 remain intact, would preserve the metal from further action ; but, 

 unfortunately, some of it usually breaks away, exposing fresh 

 surface to the injurious action, and also proving an annoyance by 

 passing through the hose and clogging the nozzle. For these 

 reasons it is best not to use these sulphur mixtures in knapsack 

 pumps.' 



* Report of the Government Entomologist for the Year 1896. Cape of Good 

 Hope, pp. 139-140. 



