468 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



It will be seen that even with the first crop there was a very 

 marked correlation between atmospheric pollution and the weight of 

 crop obtained, and, further, that the differences have become more pro- 

 nounced with each successive crop. The experiment is still in progress, 

 so that we must reserve detailed discussion of the results, but the 

 data given above may serve to show that we are obtaining proof that 

 the detrimental effects demonstrated in our earlier laboratory experi- 

 ments do actually exercise a measurable influence upon the growth of 

 plants under practical conditions in the open. 



We are also investigating further effects of atmospheric pollution 

 upon plant growth, in particular the effects upon the composition and 

 duration of growth of plants, but our observations on these points 

 are not yet ripe for discussion. 



During the past eighteen months the distribution of smoke-pollution 

 over an extensive area on all sides of Leeds has been studied, and the 

 results which will shortly be published indicate that a very wide area 

 of the surrounding country receives marked smoke-pollution from the 

 city. The detection and measurement of effects upon the crops in these 

 areas is a matter of great difficulty, since the contrasts are by no means 

 so marked as within the city, but we are hopeful that eventually we 

 shall be able to demonstrate that the farmer and horticulturist in the- 

 neighbourhood of the smoky town have a substantial grievance against 

 the smoke distributors. ' 



