Form shades like these? Pretender, where thy blush?
In three short hours shall thy presuming hand
Th' effect of three slow centuries command[39]?
Thou may'st thy various greens and grays contrive:
They are not lichens, nor like aught alive.—
But yet proceed, and when thy tints are lost,
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Fled in the shower, or crumbled by the frost;
When all thy work is done away as clean
As if thou never spread'st thy gray and green: