MACRO (Monopole, Astrophysics, Cosmic Ray Observatory) is a large area underground experiment for the detection of penetrating cosmic ray particles. For a sample of approximately 3.6 million muons, detected during various data-taking periods between March, 1989 and June, 1993, an all-sky survey for sources of excess muon flux above the expected cosmic ray background has been performed. Periodicity analyses and searches for short-term variability have been conducted for selected sources of high-energy emission. These various studies have all had negative results; that is, the muon flux seen by MACRO seems to be entirely consistent with an isotropic cosmic ray background. A high efficiency data set has been examined for variations in the muon arrival rate corresponding to seasonal changes. The preliminary results of this study are consistent with the expected seasonal variation of order 2-3%. A much longer period of data-taking will be required for a result of higher significance.
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