Definition of "durty"

"For men in stead of those magnificent Buildings which are seen in the world, could have had no better kind of dwellings then a bigger sort of Bee-hives or Birds-nests, made of contemptible sticks, and straws, and durty morter."

1662, Henry More, An Antidote Against Atheism, Book II, A Collection of Several Philosophical Writings of Dr. Henry More, p. 49