We report on 3.2 years live time of underground muon observations taken between 1981 and 1989 using the Soudan 1 proportional tube detector, located at a depth of 1,800 m water equivalent. The post-1984 observations are consistent with earlier published data on an excess signal apparently correlated with the Cygnus X-3 orbital period. The signal-to-background ratio in the entire data sample is 1 to 3 percent, depending on phase width. These data are not contradicted by other measurements. However, a larger detector will be required to establish a signal, if one exists, at a high level of certainty.
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ACKNOWLEDGEMENTS This work has been supported by the U. S. Department of Energy and the State and University of Minnesota. We acknowledge the cooperation of the State of Minnesota Department of Natural Resources, particularly the crew at Tower-Soudan State Park. This experiment would not have been possible without the enthusiastic efforts of Donald Lo-