FIELD AND FOREST. 33 



Society of Arts. The Duke of Buccleuch, K. G., took the chair, and 

 there were present representatives of the Scottish, Chesire, Warwick, 

 Hampshire and Banbury Chambers of Agriculture ; the Farmer's 

 Club, Dr. Maxwell Masters, representing the president of the Royal 

 Society, Prof. Voelcker (chemist to the Royal Agricultural Society,) 

 Mr. Sewell Reed, M. P., &c. The conference was opened by a 

 paper read by Mr. Murray. 



The paper commenced by assuming as an axiom that, besides the 

 occaisional great injury done by insects, by which whole districts are 

 ravaged, a continual drain is constantly kept up by them, which con- 

 stitutes a very perceptible percentage of deduction from the cultiva- 

 tors' profits ; and, further, that where this loss can be prevented at 

 less cost than the loss it occasions, it should be prevented. 



It next maintained that, if we wished to rid a district or a country 

 of an injurious insect, to be effective, any attempt to do so must be 

 simultaneous and combined, for to what purpose would it be if one 

 man cleared his farm if his neighbor did not clear his ; or if the one 

 cleared his one year and the other cleared his another? A central 

 authority, therefore, is needed to secure united action. 



It next considered the various ways in which the insects injurious 

 to agriculture might be extirpated. The first, the simplest, the most 

 powerful and the most efficient of these is country or district rotation 

 ot cropping. Farmers know well enough the advantage of a rotation 

 of cropping (or its equivalent) on their own farms. By long-con- 

 tinued growth of the same crop on the same land the soil becomes 

 exhausted of some of the elements necessary for the proper develop- 

 ment of that kind of crop, and a change of crops brings other ele- 

 ments into use, and relaxes the demand upon those that have been too 

 much drawn upon. 



Exactly the converse of this takes place with regard to certain in- 

 sects. The great majority of vegetable-feeding insects do not feed 

 on all kinds of plants indiscriminately ; most of them are restricted to 

 one kind of plant, and if by cultivation of that plant its numbers are 

 enormously increased, so will naturally be the number of the insects 

 that feed upon it; while, if we should cease to grow that plant, the 

 number of the insects would correspondingly diminish. Thus, for 

 instance, if a district is almost entirely in pasture, there will be very 

 few wheat-feeding insects in it, but if it is turned into a wheat country 



