Industrial melanism in England after $\displaystyle 1850$ is an excellent example of Natural selection. Explain how ?

Before industrialization thick growth of almost white lichens covered tree trunks and walls, from the mixed population of white and black winged moths white winged moth survived and increased in number due to camouflaging, dark coloured moth were picked out by predators and thus decreased in their numbers. After industrialization tree trunks became dark due to industrial smoke and soot / absence of lichen, dark coloured moth survived and increased in number due to camouflaging, white winged moths were picked out by predators and thus decreased in their numbers.