S28 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, apparently beyond the range of smoke 
damage, so that in comparing injured with 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 17 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 
67 per cent of the cases examined, however, does the ash of the injured 
trees contain a larger percentage of sulphur trioxid than that of both 
the individual uninjured trees and the averages for the uninjured 
bEGES: 
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. 
: =: 
Serial No: ae of mine furnish- Sulphur. Serinline: Name of mine furnish- Sulphur. 
ing ore. ing ore. 
Per cent.) Per cent. 
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