10, INJURY BY SMELTER WASTES. 



commonly causing the destruction of forests. These samples of 

 foliage were classified by the forester and forwarded to the Bureau 

 of Chemistry for analysis. 



For purposes of investigation samples of the dead and injured 

 trees surrounding the smelters were examined, as well as of the unin- 

 jured trees of the same species beyond the range of aj^parent injury. 

 The sulphur trioxid content of the foliage and ash of the two sets 

 of samjDles was then comi)ared. The soils beneath the injured trees 

 were compared Avith those from beneath the uninjured trees to de- 

 termine whether any increase in the sulphur trioxid content of the 

 injured trees might be due to an increased amount of sulphur trioxid 

 in the soil. 



If the sulphur trioxid content of the uninjured trees, situated much 

 farther away from the smelters, is less than that of the injured trees 

 situated near the smelters, and yet the sulphur trioxid content of the 

 soils in which the trees grow is the same, or nearly the same, in both 

 cases, this increase of sulphur trioxid must have been absorbed from 

 the air and must be responsible, wholly or partly, for the death of 

 the trees, since it is known that small amounts of sulphur dioxid and 

 trioxid, when absorbed by the leaves of trees, do kill them. In the 

 absence of insect pests in sufficient numbers to cause great injury, of 

 forest fires, or other ordinary causes for the death of trees, it must 

 be concluded that it was the sulphur dioxid and trioxid alone that 

 caused the damage. 



Attention is again called to the fact that this method of comparing 

 injured trees with uninjured trees at a greater distance from the 

 smelter is better than the method followed by the writer at Redding, 

 Cal.,<^ and should undoubtedly be folloAved in all cases where such a 

 comparison is possible. The country around the Tennessee smelters 

 easily lent itself to carrying out the investigation in this Avay, while 

 in the country around Redding, CaL, such a method of working out 

 the problem would have been extremely difficult. 



In Table II are given the results obtained by examining the foliage 

 of the injured and uninjured trees for sulphur trioxid and ash. In a 

 northerly, easterly, and Avesterly direction the Avriter collected and 

 examined samples from beyond the range of apparent significant in- 

 jury. In a southerly direction a fcAv such samples Avere collected, but 

 unfortunately they were very wet Avhen gathered and molded during 

 transit. HoAvever, since the samples collected beyond the apparent 

 range of injury in an easterly direction grcAv in a soil containing 

 practically the same amounts of sulphur trioxid as the soils south of 

 the smelters, and also since the examined area to the south is near 

 the area over which the samples were collected east of the smelters, it 



« U. S. Dept. Agr., Bureau of Cliemistry, Bui. 89. 



