The Weathering of Mortar

Abstract

MR. RICHARDSON'S letter (March 9, p. 310) anent the above calls, I think, for some further remarks. My observations never led me to conclude that the growth of moss was in any way responsible for the development of the ridge-and-ring markings upon the surfaces of old and exposed mortar. I have seldom seen moss growing thereon, but lichen is very often present, covering the whole surface, and not limited to the linear concavities. There is a row of fishermen's cottages at St. Ives, Cornwall, fully exposed to the sea, and the old mortar in the walls shows the markings in unusual perfection, but there is no evidence that moss ever grew upon it.