blue cliff coastline Cornish cornwall England english Great Britain horizon natural nature rock rocky sea shore stack tide waves background cracked geology gray grey lines sedimentary texture worn yellow cottages doors historical home house old rustic simple stone terraced white windows beach ocean sand surf surfing water cave cavern hole low tide Davidia flowerhead flowers garden ghostly handkerchief petals pocket stamens tree Michael mount national trust rockery saint spring St. Michael's Mount germander green leaves speedwell Veronica chamaedrys wild