18 



INJURY TO VEGETATION BY SMELTER FUMES. 



Of the nine different groups examined above it will be noted that 

 in only one case, the larch, is the amount of sulphur trioxid in the 

 injured tree less than that in the uninjured, and in only two cases is 

 the amount of sulphur trioxid in the ash lower in the injured tree 

 than in the uninjured. This is a somewhat better result than that 

 obtained in the investigation made in California; but it must be 

 remembered that the German forests are kept in a much better con- 

 dition than our own, dead trees being removed, etc., so that these 

 investigators did not stand so great a chance as the author of taking 

 samples from trees which had died from natural causes. 



In the following table are given the results obtained on examining 

 the trees around the smelter some three or four years later : 



TABLE 6. Result of second examination made at Letmathe about three years 

 after the one recorded in Table 5. 



