A far cicada rings high and clear over the river’s heavy wash. Morning glory, a lone dandelion, cassia, orchids. So far from the nearest sea, I am taken aback by the sight of a purple land crab, like a relict of the ancient days when the Indian subcontinent, adrift on the earth’s mantle, moved northward to collide with the Asian landmass, driving these marine rocks, inch by inch, five miles into the skies. The rise of the Himalaya, begun in the Eocene, some fifty million years ago, is still continuing: an earthquake in 1959 caused mountains to fall into the rivers and changed the course of the great Brahmaputra, which comes down out of Tibet through northeastern India to join the Ganges near its delta at the Bay of Bengal.