I have been doing some more research into the distribution of glacial erratics on and around Preseli, and this has led me to look at the locations of stones and the uses made of them over the years.
One of the great local historians, ET Lewis, mentions scattered boulders in several of his books, and says that they were more abundant on the south side of the upland ridge (as you would expect, given the directions of movement of the Irish Sea Glacier) than to the north. Where they were present in abundance, they were often considered a nuisance, since they had to be cleared from fields, and they were of course often used in the construction of walls, houses and farm buildings.
Lewis, in his many mentions of cromlechs, standing stone settings and circles, does not mention a single case of stones having been transported from some "special" place. He simply assumes that the stones were always used where they were found, and there is no sign that spotted dolerite, for example, was more valued than local volcanic ash, or unspotted dolerite, or slate or shale. Utilitarianism and opportunism ruled, as it does in the vast majority of building projects today. So the most famous prehistoric monuments, including Bedd Arthur and the Gors Fawr circle, are made with unspectacular stones collected up in the immediate vicinity. That having been said, of course, we cannot disprove the possibility that at some stage some builder was obsessed enough with a particular stone type to go to great trouble to go off and get it, with considerable expenditure of time and effort. All we can say is that there is no evidence, as far as we know, to support that theory.
In his book on Mynachlogddu, Lewis mentions that in the period 1800-1920, when heavy gates were being installed and used on a large scale, big stone pillars were needed as gateposts. He says they may now be found "by the hundreds over a radius of about ten miles." A favourite place for collecting them in the early twentieth century was Carn Goedog, where they were picked up or levered away from the rock outcrops and taken away on sledges. It's clear from his description that although Carn Goedog is on the north flank of the mountain, stones were dragged up over the ridge and down to the farms on the south side, in Mynachlogddu and neighbouring communities. Carn Goedog provided the stone for the facing of the Congregational Chapel in Felindre, and stone from"the lower slopes of Carnmeini" were used for the bulding of Bethel Baptist Chapel in Mynachlogddu.
We have mentioned some of this before, with a reproduction of an article by my colleague Dyfed Elis-Gruffydd:
ET Lewis also mentions a number of named tracks over the mountain, which can still be seen. However, we should not assume that these were used primarily for the "stone trade" -- some of the greatest impacts on the landscape were made by the thousands of animals which were moved across the mountain ridge during the droving era, and Lewis says that he talked to old residents who could remember (prior to 1913) "a dozen carts at a time" going to the Carn Goedog district to collect peat from the traditions peat-cutting areas.
Here are some descriptions of the old farm vehicles:
1796 Near Tavernspite, Pembrokeshire
The women join more in the labours of the field than in England, a man holds the plough drawn by four horses, but oftener by six oxen, and a girl drives them, sometimes riding upon one of them ; the men more commonly drive the carts, and Weanes (in a wain the weight of the fore part rests by a pole upon the yoke of the oxen) but the girls and women usually ride a horse dragging a kind of sledge, also used in Scotland, it consists of two long sides (rather shorter than in Scotland) one end of which serves for the shafts, the other rests upon the ground, it has cross bars, and two uprights are fixed near the bottom, on which is laid whatever is meant to be conveyed.
Lady Sykes, typescript copy of a tour of Wales, University of Hull, DDSY(3)/10/11, p. 151
A farming party also appeared at this instant, proceeding with goods for Carmarthen market. … A sledge loaded with sacks of grain followed; … But a word on the sledge, the common farming carriage in Wales. This is a most simple contrivance, consisting of two rude poles between which the horse is placed; their ends trail on the ground, towards which extremity there are two or three cross bars; a few upright sticks from these complete the carriage. A comely dame, seated on horseback, and accommodated with a sort of side saddle made with cross rails, was probably the mistress; she closed the rear; and her superior condition was evident, in her dark blue worsted stockings, ponderous shore and small brass buckles.
Barber, J.T., (1774-1841), Tour Throughout South Wales and Monmouthshire, Comprehending a General Survey of the Picturesque Scenery, Remains of Antiquity, Historical Events, Peculiar Manners, and Commercial Situations of That Interesting Portion of the British Empire. (1803), p. 40-41
1815 (about), south Wales
Original vehicles for corn and hay are still used in some parts of the uplands.
(1) Wheeled cars, having one part sliding on the ground and the other mounted on a pair of low wheels
(2) drag car
(3) dorsal car, the sliding part as in the two former vehicles shod with thick wooden slippers, and shafts suspended from the horses back. …
Wagons are partially used on more level lands, but the Scottish cart is growing into common use.
Evans, Thomas, Walks through Wales, (post 1816), pp. 56-57; Evans, T., Cooke, G.A., (editor); Topographical and statistical description of North Wales [1830s], pp. 56-57
On the basis of the foregoing we can suggest the following:
1. Stones that were suitable for building into prehistoric or historic structures were simply collected and used close to the places where they were found.
2. Carn Goedog was a major source of elongated pillars during the nineteenth century (and probably not before and not much afterwards) when there was a strong demand for heavy gateposts capable of supporting heavy gates.
3. The network of trackways on Preseli is partly related to stone collecting, but most tracks are the result of peat-collecting activities and droving traffic.
4. Historical references suggest that stones were collected from the lower slopes of Carn Meini, and not from the highest crags.
5. The term "quarrying" should not be used here at all. The term "stone gathering" or "stone collecting" is much more appropriate. There is nothing to suggest that explosives or any mechanical devices were ever used to take monoliths from rock faces.
6. There is no reason to think that Carn Goedog was ever used as a prehistoric quarry or "supply point" for monoliths intended for long-distance transport. It will naturally have been used as a source for small stones needed for the huts, embankments, circles and enclosures found within a short distance of the outcrop.
Here is a nice illustration of the various Irish slipes and slide-cars known from the rural districts where land was rough. Note that different models were used for different loads. I assume that the Welsh versions will have been similar......
None of these had anything to do with transport over snow and ice. They were used throughout the year.