82 Caterjyillars on Oak 



was an experimental lot, and cost £5 per cwt. One pound of the paste 

 was used to about 30 gallons of water, this giving 1 lb. of lead chromate 

 to every 60 gallons of spray. 



Messrs Merryweather of London supplied us with a 3 h.p. petrol 

 driven pump with sufficient metal piping and flexible tubing to reach 

 right across the plantation. Six jets were available and with the pump 

 working at full pressure each jet was spraying about one gallon per 

 minute. (See Plates III, IV, V.) 



About twenty students and others from the college were present 

 to do the spraying, and mix the material. 



Considerable time was spent in moving the engine and laying out 

 the mains ; rain delayed matters, and only about eight hours during 

 the two days were actually spent in spraying. 



The water was supphed in water carts by the park authorities, and 

 a second petrol pump was used to pump it into the galvanised iron 

 tanks in which the spray was mixed. Two of these tanks were used, 

 each holding about 30 gallons of water, and as one was being emptied 

 the spray was made up in the second. One pound of paste was softened 

 in a bucket with warm water from the engine and diluted down to 30 

 gallons. In this way the solid matter was obtained in a very fine state 

 of suspension, forming an admirable spray to work with. No trouble 

 was experienced due to the paste settling to the bottom of the tanks. 



During the two days some 1700 gallons of spray were used, practi- 

 cally every tree being reached. The pressure however was quite in- 

 sufficient to drive the spray to the tops of the oaks. On the second day 

 a fire escape was provided and with its help many of the tallest trees 

 were thoroughly sprayed all over (Plates VI, VII). The days chosen 

 for the spraying were the only ones available, and there is little doubt 

 that at least a week later would have been better as then the trees 

 would have presented a much larger area of foliage. Moreover the 

 leaves being more fully grown would not so readily have caused the 

 breaking of the film of spray (viz. solid matter from the spray) by their 

 expansion, as actually was the case. On the other hand the caterpillars 

 would have been older and hardier at this later date. 



The attack of caterpillar has, throughout the park generally, been 

 very shght this year and the damage up to the end of June inconsiderable, 

 though one or two trees were noticed which either on account of cater- 

 pillars or for some other reason never from the beginning appeared to 

 have the normal amount of foliage and presented a very bare appearance. 

 Nor can it be said that the Ham Cross Plantation fared better or 



