Robert Murray, Sandbelters: Memories of Middle Australia (Australian Scholarly Publishing, 2011), 211 pages, $34.95. Robert Murray’s memoir, Sandbelters, is self-effacing and well-mannered, a relief from the prevalent tell-all memoirs. It will be a rich lode for other social historians, although the index, alas, is perfunctory.   A regular contributor to Quadrant on history and politics, Murray at eighty maintains a prolific output. His landmark works were The Split: Australian Labor in the Fifties (1970) and 150 Years of Spring Street (2007) on Victorian state governments. But Murray has written a dozen other histories of institutions, places and industries, and he…