Read it through once

If one scrambles to the top of one of these heaps, it is easy to see all the details of the occupation. Long underground runners of coltsfoot and of horsetail are climbing up the sides, fringes of creeping buttercup, couchgrass, and other hardy weeds occupy, every year, a little more of the flanks, but, on the top, one very soon finds that the dust of the atmosphere, aided by weathering, has afforded a chance to mosses, to hawkweeds, and other rock plants. These in time cover the top, and soon hardy grasses and weeds form a regular turf on the top of the shale.