14 THE SMOKE INVESTIGATION 



winds may be understood (Fig. 2). The particular 

 regions of the Aliquippa district to which attention is to 

 be directed may also be seen by referring to this map. 

 These regions were selected in order that a number of 

 different conditions might be secured. They were as fol- 

 lows : Eegion 1 is on the spur of the hill extending south- 

 ward toward the mill and about 1500 feet a little northwest 

 of the mill. Region 2 is about one-half of a mile north 

 of region 1 and, on account of the prevailing winds, re- 

 ceives very little smoke and fumes from the mill. Region 

 3 is approximately 900 feet west of region 1. Region 4 

 is about 1,300 feet northwest of region 3 on the slope of 

 the hill and seemed to be well protected from the smoke 

 and fumes from the mill. Region 5 is on the slope of the 

 hill near the Pittsburgh & Lake Erie Railroad and about 

 1,500 feet southwest of the mill. Region 6 is in the valley 

 near the mill and receives the full effect of the sraoke and 

 fumes. The mill referred to is Jones and Laughlin, which 

 has been established there since 1909. 



Besides these blast furnaces, there are railroads on 

 either side of the river over which trains run at frequent 

 intervals. The prevailing winds, being northwest, are 

 effective in carrying smoke and gases from the trains and 

 furnaces, resulting in the destruction of most of the trees 

 on the hillside and ravines east of the river. On the west 

 side of the river rather extensive observations were made 

 in the regions corresponding approximately to the numbers 

 on the map (Fig. 2). In these regions, studies of annual 

 rings and of the anatomical structure of leaves were made. 

 Realizing that anything which would cut off the food 

 making in the plant would diminish the width of the an- 

 nual ring and that this might be produced by an accidental 

 breaking of a limb or top of a tree, the writer took cross sec- 

 tions of the stems at different points, as Figs. 5-14 will 

 show. It was found that in region 4 no noticeable injury 

 could be detected either in the general character of the trees 

 or in the width of the annual rings. The difference in width 

 of annual rings was found to be well marked in certain 



