THE SMOKE NUISANCE 247 



impurities, that crops of radishes and lettuce grown in different sections 

 of Leeds show the possibility of correlating the known atmospheric 

 impurities with the yield of the crop. They also found that as trees 

 automatically keep a record of yearly growth, the presence of any inhib- 

 iting factor will make itself known by the narrowing of the annual 

 rings. 



In 1913, a study of the effct of city smoke on vegetation was made 

 in Des Moines by A. L. Bakke, of the Iowa State College. 4 Mr. Bakke 

 reached the following conclusions: 



1. That gases and smokes have a deleterious action upon vegetation. 



2. That the vegetation about a manufacturing concern may be 

 mapped off, in the form of concentric belt demarcation, each belt being 

 represented by a certain form or forms of plant life, since certain plants 

 are more susceptible to smoke injury than others. 



3. That an industrial city like Des Moines, in its plant elimination 

 process, is governed by the same set of conditions as are in operation for 

 a single manufacturing plant. 



Mr. J. F. Clevenger, as a result of his studies in connection with 

 the Smoke Investigation of the Mellon Institute, declared that the fact 

 that smoke injures vegetation is evidenced not only by the general ex- 

 ternal appearance of many of the constituent plants, but also by their 

 internal appearance, as shown by the size of annual rings and by lesions 

 in the leaves. 5 Mr. Clevenger's studies were confirmed by controlled 

 field experiments which he made. In these experiments growing plants 

 enclosed in cases were subjected to small quantities of soot distributed 

 uniformly over them. The leaves of the plants so treated displayed a 

 tendency to drooping and many of the leaves began to die at the tips; 

 a checking of growth of the plants was also apparent. 



The effect of smoke on health has been a much-mooted question. 

 For a long time it was held, and still is by some, that a smoky atmos- 

 phere is not injurious and at times even beneficial to public health. 

 This supposition gained favor from an observation, largely erroneous, 

 that coal miners are not prone to contract tuberculosis. 



One of the most comprehensive studies of the -direct effect of smoke 

 upon the respiratory organs was made by Dr. Louis Ascher, of Konigs- 

 berg. Dr. Ascher's statistical and experimental studies led him to the 

 conclusion that the mortality of acute lung diseases is certainly in- 

 creasing, especially among children and old people. The cause of this 

 increase, he declared, is the impurification of the air by smoke, as the 

 increase is greatest in industrial centers and not in agricultural districts. 

 He further pointed out that within industrial districts a difference in 



4 Bakke, A. L., "The Effect of City Smoke on Vegetation," Bulletin 145, 

 Iowa State College of Agriculture. 



5 Clevenger, J. F., Bulletin No. 7, "The Effect of the Soot in Smoke on 

 Vegetation," 1913. (Published by Mellon Institute.) 



