AT the south-east corner of Glasfryn lake, in the parish of Llangybi, is a well called Ffynnon Grassi, or Grace's Well. In the olden time it was a fairy well, and Grassi was in charge of it. Her duty was to keep the cover always on the well, except when water was being drawn. One evening she forgot to close the well, and the water gushed out. It flowed strongly and ceaselessly, but so noiselessly was the flow that the fairies did not notice it. At last it overwhelmed one of their dancing rings, and they perceived and stopped the overflow, not, however, before Glasfryn lake had been formed.
When she saw the result of her negligence, Grassi, overcome with remorse, walked to and fro on the piece of ground which is now called Cae'r Ladi, "the Lady's Field," wringing her hands and weeping and moaning. The fairies seized her and changed her into a swan. In this form she haunted the lake which her forgetfulness had caused for six score years, after which time the fairies allowed her to resume her human shape. At any rate, there is to be seen about two hours after midnight, on certain nights in the year, a tall lady with lovely features and large bright eyes, dressed in white silk and a white velvet bonnet, wandering up and down the high ground of Cae'r Lath, weeping and wailing. If she is not Grassi, who is she?