Welsh Journals

became very heavy about 2 p.m., the fall being great on the hill known as Carmarthen Fan, between the two lakes, so that the water came down the Sychlwch, but affected its neighbour the Sawdde very little. The stream rose 4 feet in 15 minutes. From the summit and slopes of the cliffs masses of peat and sandstone were torn, leaving hollows 2 to 3 feet deep, while a new channel for the stream 10 feet deep in places was cut in the valley itself, while boulders and sand were piled up elsewhere in banks 10 feet high. "At the height of the storm," says Mr. D. A. Howell, the engineer, the crashing of the huge boulders and the lashing of the rain created an uproar which completely drowned the noise of the thunder." The storm had ceased by 2.45 p.m. It will be seen that the general results were similar. They were intensified at Llyn-y-fan-Fach in that the storm broke at the top of the scarp, and therefore the slope was greater. The main points of interest seem to be as follows:- (a) The protective character of even a thin turf it threw off the water from the Fan Llia with little erosion except where cut through by the drains for the trials. (b) Slope is of prime importance in denudation the work done along the graded stream to the Llia obliquely across the slope was small compared with that along the main catchment drain directly down the slope. (c) The amount of destruction possible in a brief space of time. This is a point to be specially remembered when con- sidering the evolution of surface features. Here it is best seen in the cutting of a new valley and the marked lowering of the stream bed of the Llia near Mellte Bridge. (d) The weight of the stones lifted, e.g., the four biggest noted are calculated to weigh--one 10 cwts., one 28 cwts., and two between 31 and 35 cwts.