16 THE SMOKE INVESTIGATION 



Elms and Pines. The sections of Elm taken at region 

 6 show a decided narrowing of the rings for the last three 

 years corresponding with the time that the mill has been 

 established in the neighborhood (Fig. 5). When these 

 sections are compared with sections of a similar tree ob- 

 tained at State College, it will be found that this feature 

 is lacking (Fig. 7) ; here the tree was in a favorable place 

 for growth. Fig. 6 illustrates sections of an Elm obtained 

 from region 5, Aliquippa district, which show evidence of 

 injury due for the most part, in all probability, to the 

 smoke and gases from the trains which run at frequent 

 intervals. Fig. 8 shows sections of Elm obtained from 

 the hillside at Nine Mile Run which bear evidence of 

 smoke and gas injury. This is shown by the irregular 

 and narrow annual rings. It indicates, furthermore, that 

 the young trees are injured less than older ones, thus ac- 

 counting for the presence of a number of scrubby plants 

 in many places. 



The same general conditions are found when cross 

 section of Hicoria collected at region 3, Aliquippa dis- 

 trict, are compared with similar ones collected at Nine 

 Mile Run and on the mountains near State College (Figs. 

 10, 11, 12). 



When sections of pines collected from region 3 are 

 compared with similar ones collected in the mountains 

 near State College it will be found that this narrowing 

 of annual rings is present in the former, while a wide 

 uniform annual ring is seen in the latter (Figs. 13, 14). 

 A locust, which is commonly thought to be and apparently 

 is sensitive to the effects of smoke and gases, found grow- 

 ing in region 4, bears evidence of this narrowing of an- 

 nual rings (Fig. 9). Other plants in this region did not 

 show this condition. At a distance of 1,500 feet from 

 the mills very little of this effect could be observed and 

 is explained of course on the ground that the winds blow 

 the major part of the smoke and gases away from the sta- 

 tions. A large number of wood sections were examined 

 and Figs. 5-14 are a fair representation of the lot. They, 

 for the most part, tell their own story. 



