There was a time when the reach of China penetrated deep into Siberia with its peoples owing allegiance to its distant Emperor. Then rapidly in the seventeenth century, the Russians arrived. At first, the ensuing conflict went primarily in the direction of China but Russia's growing power and the Qing dynasty's slow unraveling tipped the balance in the direction of Russia, finally settling on a boundary that for hundreds of miles is marked by the Amur River. Yet it remains unsettled. Though on the surfaces of global diplomacy all is well between China and Russia, the communities adjacent to the river tell a different, more uneasy story. Colin Thubron at eighty, having been an accomplished traveler in and chronicler of both countries decades before, travels in his latest book, 'The Amur River: Between Russia and China' down its length, acutely observing and beautifully describing, amongst much else, these anxieties, these differences. The first most obvious is how th...