The ''mysterious experience'' on Beinn Dronaig described by Charlie Stephen in his letter in the June issue reminds me of something similar which I experienced many years ago at Annet, at the head of Upper Loch Torridon.
It was in 1936 or 1937, on a fine September morning while I was staying there on a walking holiday with friends. We were alerted by a sound, rather like the noise of a train approaching a station on the London tube railway; this sound appeared to be coming from the range of hills on the southern side of Glen Torridon. As the sound got louder and nearer the whole landscape shimmered as if out of focus; this lasted for a few seconds. Although I was not conscious of any movement of the ground there obviously must have been some vibration.
I was told at the time that earth tremors along the fault lines in the Western Highlands are not uncommon. I have been back to the North-West many times since but have never had a repeat of this experience.
W. H. . McLeod.