14 BULLETIN 672, IT. S. DEPARTMENT OF AGRICULTURE. 
Another theory that attracted much attention was the supposition 
that the birds were poisoned by sulphurous or sulphuric acid resulting 
from waste from the great smelters near Salt Lake City. It was 
believed that sulphur from the smelter smoke, depositing on vegeta- 
tion, was washed into the streams and marshes by rains, and that 
in combination with moisture it formed sulphurous and sulphuric 
acid. It was supposed that the ducks in feeding found this in 
quantities sufficient to be fatal. It was found, however, that small 
quantities of these acids, diluted as they must be in nature, had no 
effect upon ducks, and birds were able to withstand for a con- 
siderable period solutions strong enough to be very sour. In these 
experiments the characteristic appearances and actions of the 
duck sickness were not produced. Further, the fact that the sick 
birds are found in the Tulare basin and elsewhere where there are 
no smelters, and where there is no other appreciable trade waste 
of sulphur, serves at once to refute this theory. 
Many contended that waste water from the settling ponds of the 
sugar factories was at the bottom of the trouble. This seemed 
plausible, as sugar factories are located on each of the three rivers in 
Utah on whose drainage sick ducks occur. Those who supported 
this theory attributed the affection either to sulphuric acid used in 
great quantities in the factories and allowed to escape through drains, 
or to toxic matter from bacterial agencies generated in the catch 
ponds that receive the factory drainage. The first supposition has 
been shown to be untenable. As regards the second, the drainage 
from these ponds enters the rivers in quantity only during the season 
that the factories operate in fall. By the time this drainage reaches 
the marshes in abundance few ducks are dying, and finally the mor- 
tality ceases while the mills are still in operation. In 1914, drainage 
from these settling ponds emptying into the Weber came down with 
the rise in the water level consequent upon the cessation of general 
irrigation in mid-September, and there was sufficient toxic matter 
present to kill large numbers of carp and chubs in the lower channels. 
Many fish-eating birds (all subject to the duck sickness under proper 
conditions) were attracted by the abundance of fish floating helpless 
on the water and fed here until these fish disappeared, but no birds 
were found sick. During late summer many sick ducks had been 
found along the lower reaches of the Weber where it spreads out on 
the lake front, but with this rise in the water, conditions among the 
ducks improved immediately. As in other cases the fact that the 
duck sickness occurs in areas where there are no sugar factories serves 
to militate against the theory that toxic matter in factory drainage 
is the cause. 
In addition to these, the trouble has been ascribed variously to the 
presence of sewage in the water, parasitic nematodes, arsenic poisoning, 
and other minor hypotheses, none of which has been found tenable. 
