It's possibly a bit cheeky to add this as I don't know where it is. But let's face it, it's unlikely to have wandered off somewhere. And while large rocks like Allt an Airgid exist very nearby, I'd dearly like to think this is somewhere around too, and not so far from the circle at Killin.
I have scoured the 25 and 6 inch maps for a sign without luck. But we do know that it is/was on the estate of Auchmore House (now demolished) and it was in woodland. There's an offputting amount of forest today, but 100 years ago it was mostly confined to the area north of the road: see here for example.
The other stone ... to which I alluded to is in the woods of Auchmore at Killin... This stone is called Fuaran na Druidh Chasad, or the Well of the Whooping-Cough. I heard of it ... from a native of Killin, who remembered vividly when a boy having been taken to drink the water in the cavity of the stone, in order to cure the whooping-cough, from which he was suffering at the time. Happening to be in Killin lately ... I made inquiries in the village; but though some of the older inhabitants remembered having heard of the stone, and the remarkable practice connected with it, I could not get any one to describe the exact locality of it to me, so completely has the superstition passed away from the mind of the present generation. I went twice in search of the stone; and though, as I afterwards found, I had been within a very short distance of it unawares on both occasions, I was unsuccessful in finding it. At least I met an old man, and after some search we found the stone, and he identified it.From 'Notice of two boulders having rain-filled cavities...' by H Macmillan, in the Proceedings of the Society of Antiquaries of Scotland, v18 (1883-4).
I understood then what had puzzled me before, viz., why it should have been called Fuaran or Well, for I had supposed it had a cavity in a stone like that at Fernan. It was indeed a cavity; but it was in the projecting side of the stone, not on its top surface. It consisted of a deep basin penetrating through a dark cave-like arched recess into the heart of the stone. It was difficult to tell whether it was natural or artificial, for it might well have been either, and was possibly both; the original cavity having been a mere freak of nature - a weather-worn hole - afterwards perhaps enlarged by some superstitious hand, and adapted to the purpose for which it was used.
Its sides were covered with green cushions of moss; and the quantity of water in the cavity was very considerable, amounting probably to three gallons or more. Indeed, so natural did it look, so like a fountain, that my guide asserted that it was a well formed by the water of an underground spring bubbling up through the rock. I said to him, "Then why does it not flow over?" That circumstance he seemed to regard as a part of its miraculous character to be taken on trust.
I put my hand into it, and felt all round the cavity where the water lay, and found, as was self-evident, that its source of supply was from above and not from below; that the basin was simply filled with rain water, which was prevented from being evaporated by the depth of the cavity, and the fact that a large part of it was within the arched recess in the stone, where the sun could not get access to it. I was told that it was never known to be dry - a circumstance which I could well believe from its peculiar construction.
The stone, which was a rough irregular boulder, somewhat square shaped, of mica schist, with veins of quartz running through it, about 8 feet long and 5 feet high, was covered almost completely with luxuriant moss and lichen; and my time being limited, I did not examine it particularly for traces of cup-marks. There were several other stones of nearly the same size int he vicinity, but there was no evidence, so far as I could see, of any sepulchral or religious structure in the place.
There is indeed a small, though well-formed and compact so-called Druidical circle ... within a short distance on the meadow near Kinnell House ...
... The superstition connected with it has survivied in the locality for many ages. It has now passed away completely, and the old stone is utterly neglected. The path leading to it, which used to be constantly frequented, is now almost obliterated. This has come about within the last thirty years, and one of the principle causes of its being forgotten is that the site is now part of the private policies of Auchmore.
The landlady of the house at Killin, where I resided, remembered distinctly having been brought to the stone to be cured of the whooping-cough; and at the foot of it, there are still two flat stones that were used as steps to enable children to reach up to the level of the fountain, so as to drink its healing waters; but they are now almost hidden by the rank growth of grass and moss...
If it was to be found, I think the description is detailed enough that you would be sure. There is a slightly unenlightening picture in the scan at the ADS website.
Posted by Rhiannon
11th September 2012ce
Edited 12th September 2012ce