Woburn Experimental Fruit Farm. 



5 5 



The eight report, by the Duke of Bedford, K.G., and Mr. 

 Spencer U. Pickering, F.R.S., on the work of the Woburn 

 Experimental Fruit Farm, deals entirely 

 Report of the Woburn with insecticides and fungicides, and 

 Experimental Fruit furnishes a detailed account of the very 

 Farm. valuable investigations carried out at this 



station. It is remarked in the opening 

 chapter that the aim has been to substitute as far as possible 

 exact quantitative measurements for those more crude and 

 unsatisfactory methods usually adopted, in which the impression 

 produced on the mind of the observer is the sole standard by 

 which the success or failure of an insecticide is gauged. The 

 principle adopted has been to ascertain what is the action of an 

 insecticide when it is applied under the simplest and most perfect 

 conditions possible, as in the laboratory, and then to ascertain 

 the results when it is applied in the plantation under ordinary 

 conditions of practice. Besides investigations into the effect 

 of certain insecticides, the report contains an account of 

 an examination of the nature of the substances constituting 

 some of these insecticides, which, in the case of emulsion, has 

 resulted in the introduction of a class of emulsiflers which may 

 be substituted with great advantage for soap and such like 

 substances, especially in cases where soap causes much trouble 

 and inconvenience ; whilst an investigation into the chemistry 

 of Bordeaux mixture has resulted in showing how the cost of 

 that substance may be reduced by three-fifths without in any 

 way diminishing its effectiveness. 



Bordeaux Mixture. — The investigation into the nature of 

 the compounds formed by the action of lime on copper sulphate 

 has shown that as many as six different substances may be 

 present in Bordeaux mixture. That which is present when the 

 mixture is made in the ordinary way, by adding excess of lime 

 in the form of milk to copper sulphate, is a double basic sulphate 

 of copper and calcium. The carbonic acid of the air acts on 

 this, forming carbonates and sulphates of the metals, and it is 

 owing to the gradual reformation of sulphate of copper in this 

 way, that the mixture possesses fungicidal properties. But 

 the basic sulphate of calcium present has to be decomposed 

 before the basic sulphate of copper is attacked, so that a certain 

 time always elapses before the mixture begins to behave as a 



