In the mountains where I used to live, once I went to the market to buy oranges, and a woman vendor told me the sweetest varieties come from groves whose roots reach back centuries in the soil. She said the original tree was cut down in heaven. It fell to earth and sank through horizon after horizon. Topsoil is exposed to the greatest degree of weathering. Silt, sand, wild grass, particles of clay. Cake layer of humus: nitrogen rich from the decomposition of plants and animals. We never see how deep a geology. How each burnished slice in our mouths is a key to that first treasure.