28 



INJURY BY SMELTER WASTES. 



In the preceding table, with possibly two exceptions, the soils near 

 the smelter contain practically the same amount of sulphur trioxid 

 as the soils farther away, ai:)parently beyond the range of smoke 

 damage, so that in comparing injured Avith uninjured trees, the soils 

 in which they grew need not be considered as a factor. 



Of 18 comparisons of injured and uninjured trees it will be noted 

 that in 16 cases, or in 89 per cent of the examinations made, the sul- 

 phur trioxid content of the injured trees is larger than that of the 

 individual uninjured trees, and also exceeds the averages for the un- 

 injured trees of the same species situated beyond the range of signifi- 

 cant damage. In IT cases, or 94 per cent of the examinations, the sul- 

 phur trioxid content of the ash of such injured trees is larger than 

 the average sulphur trioxid content of the ash of similar uninjured 

 trees situated beyond the range of significant damage. In only 15 

 cases (83 per cent of those examined), however, is the sulphur tri- 

 oxid content of the ash of such injured trees larger than both the 

 sulphur trioxid content of the ash of the individual uninjured trees 

 and the averages for the same. 



In a northerly direction, in 83 per cent of the cases examined, both 

 the leaves and ash of the injured trees contain a larger percentage of 

 sulphur trioxid than the leaves and ash of the uninjured trees, both 

 as regards individual and average data. 



In a southerly direction, in 83 per cent of the cases examined, the 

 leaves of the injured trees contain a larger percentage of sulphur tri- 

 oxid than the leaves of uninjured trees, and in 100 per cent of the 

 cases the ash of such injured trees contains a larger percentage of sul- 

 phur trioxid than the average ash for the uninjured trees. In only 

 07 per cent of the cases examined, however, does the ash of the injured 

 trees contain a larger i:)ercentage of sulphur trioxid than that of both 

 the individual uninjured trees and the averages for the uninjured 

 trees. 



In a westerly direction, in 100 per cent of the cases examined, both 

 the leaves and ash of the injured trees contain a larger percentage 

 of sulphur trioxid than the leaves and ash of uninjured trees. 



Since the above discussion shows that the trees around the Washoe 

 smelter are evidently injured by sulphur dioxid, it becomes necessary 

 to prove that this compound is given off from the smelter. Several 

 samples of ore from mines that supply the smelter were examined and 

 the following amounts of sulphur were found: 



Table IV. — Sulphur content of ore samples. 



