123 



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

 more Hues 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 insecticides 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 durabilicy, 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 con- 

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

 number of Vermorel knapsack pumps, in which a circuhr 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 atten- 

 tion 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 mix- 

 ture and Paris green, and these preparations are also injuriously affect- 

 ed. But even copper tanks are not suitable for use with all spraying 

 mixtures, since this metal is acted upon by the sulphur in such com- 

 pounds 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.' 



III. — Simplicity. — All the parts of the pump should be readily 

 accessible and removable, so that, should anything go wrong, they may- 

 be taken to pieces and cleaned, or damaged parts renewed. The want 

 of these facilities is a serious fault in many machines, the slightest 

 injury necessitating the sending of the whole apparatus to the repairers. 



IV. — The production of a Uniform and Effective Spray. — The 

 continuity and force of the flow is dependent upon an air chamber in the 

 pump, this feature constituting a ' force-pump.' On this account all 

 hand syringes are almost useless. The nature of the spray is regulated 

 by the form of nozzle employed. The chief object is to break up the 

 liquid into such a fine spray that it will penetrate the thickest foliage in 

 the form of a dense mist and come in contact with every part. For 

 this purpose one of the ' cyclone nozzles ' is most admirably adapted. 

 But where it is necessary to throw the liquid to a considerable distance, 



* Report of the Government Entomologist for the year 1896, Cape of Good 

 Hope, pp. 139-140. 



