This was formerly a sandstone quarry.
Before that, as shown on the 1:10560 OS map from 1864, there was a small hill called Fairy Knowe at this location ("knowe" is equivalent to "knoll"), with a summit height of 574 feet; there was, as yet, no quarry here. The equivalent maps from 1899 to 1932 show the quarry eating away at the southern face of the Knowe, and expanding from there. I have used the title "Carman Quarry", because that is what appears on present-day mapping, but it should be noted that it this was a later name; it was originally called the Fairy Knowe Quarry.
I.M.M.MacPhail's booklet "Off the Main Road" (1976) discusses the quarry at the site of the former Fairy Knowe; the author notes that "the hillside has been altered considerably by extensive quarrying and the old name, Fairy Knowe, seems now a misnomer." The author goes on to state that "it was also in more recent times known as Mount Mallow".
That last part is, I believe, incorrect: Mount Mallow (pronounced like the word "allow", but with an "m" prefixed) is a name that is now commonly applied to nearby Carman Hill, but it originally applied to the next peak to the north. Interestingly, the name "Mullour" is shown there on the 1:25000 OS map (also, the variant spelling "Millaur" was recorded in the OS Name Books), and "Mount Mallow" probably represents a vague local memory of that name. For more on this topic, see NS3680 : Moorland near Mullour on Overton Muir
The name Fairy Knowe may be an indication of what Joseph Irving, writing in 1879, described as "a once popular superstition which still lingers in the locality"; see NS3875 : Havoc Hole
for more details. In the same work, Irving also wrote that Carman Hill is "celebrated in the superstitious legends of the district". He does not give the details of these legends, but (as will be explained below) they are likely to have been connected with the Fairy Knowe, which, as my photograph shows, is located on the lower slopes of Carman Hill.
In a passage cited in one of the more recent local histories, I came across what is probably an early reference to the same beliefs: one of the works of the local author Tobias Smollett (NS3977 : The former site of Dalquhurn House
, NS3878 : Latin inscription on the Smollett Monument
) was the epistolary novel "The Expedition of Humphrey Clinker" (1771). In it, he has one of his characters write that "the fairies dwell in a hole of Kairmann(*), a [mountain] hard by"; that passage goes on to describe some of the associated superstitions.
[(*) Whyte and MacFarlan's 1811 survey of agriculture in the County of Dumbarton mentions, in a list of places in which limestone can be found, "Cairman in Cardross", a useful record of a form intermediate between Smollett's "Kairmann" of c.1771 and the spelling "Carman" that is found on OS maps from the first edition (c.1860) to the present day.]
Smollett mentions a number of unrelated traditions in the same passage. Several of these are attested elsewhere (for example, Smollett's character writes that "Loff-Loming", i.e. Loch Lomond, "has got waves without wind, fish without fins, and a floating [island]"), so it is likely that the words quoted above are an authentic record of local belief, rather than being the author's invention.
The Fairy Knowe must have been given its name for a reason: logically, the above-mentioned hole of Carman was located there.
Another faint echo of these superstitious beliefs is to be found in the following old couplet, recorded by Irving (see above):
"In at the flow of the Havock,
and out at the yetts o' Carman".
The first part of the couplet undoubtedly refers to a cave, NS3875 : Havoc Hole
(see that item for more information). In the light of what Smollett wrote, it is probable that "the yetts [gates] of Carman" were a corresponding opening in the Fairy Knowe (on Carman Hill). The opening was apparently thought to lead to, or at least to communicate in some way with, the cave at Havock; that cave was, according to Irving, "reputed at one time to have been a favourite resort of the Lennox witches" (see the last-cited link for the reference). The only traditions now referring to the cave at Havock are ones about William Wallace (faint echoes of similar supernatural traditions are associated with a different cave a few miles from there; it is not clear whether these were transferred from Havock, or whether they are quite independent of it).
Another belief is also worth mentioning here: the nearby hill-fort on the summit of Carman Hill was only identified from aerial photographs as recently as the 1950s. However, the prominent boulders (NS3779 : View over ancient hill-fort
) that lie within its boundaries had not previously escaped notice; in the second half of the nineteenth century, the popular belief was that those stones had been set there by the Druids.
The colour of the underlying soil is best seen in the mound at the right-hand side of the photo. That mound is not the Knowe. The latter was much larger: it embraced all of the green area that appears in the foreground and middle distance of the photograph, and more besides. To the north, it extended to the line of trees that can be seen in the middle distance. Those trees stand on top of a crescent-shaped ridge that separates the green edge of the quarry from the brown hillside behind it. The ridge is a remnant of the Fairy Knowe; in fact, it is what remains of the northern edge of the Knowe: NS3679 : Northern edge of the Fairy Knowe
Some features of geological interest can still be seen in the old quarry: NS3678 : Traces of ancient mud cracks
To the left, the hill in the background is Carman Hill, and the "bump" visible to the right of its summit is the location of some boulders that lie within an ancient hill-fort: NS3779 : Ancient hill-fort on Carman Hill