From Phil Morgan:
As you well know I am a member of the 'human transport' camp and I have pondered the problem of how our ancestors may have navigated the route if the bluestones were transported overland. While driving from the Midlands to south Wales, along the M50 there was an excellent view of the Black Mountains, which prompted the following:
The co-ordinates below are for the end points of sightlines and are taken from 'Where's the path?' on the Internet.
a). Amesbury to Milk Hill, (240 metres, 51.376549, -1.850252) = 14 miles apart;
b). Milk Hill to the Malvern Hills, (400 metres, 52.104766, -2.338886) = 32 miles .. ;
c). Malvern Hills to Hay Bluff, (700 metres, 52.009586, -3.086171) = 40 miles .. ;
d). Hay Bluff to Pen y Fan, (860 metres, 51.883511, -3.436704) = 17 miles .. ;
e). Pen y Fan to Fan Brycheiniog, (780 metres, 51.881021, -3.707156) = 12 miles .. ;
f). Fan Brycheiniog toTrichrug, (400 metres, 51.890319, -3.891735) = 8 miles .. ;
g). Trichrug to Pen-crug-melyn, (300 metres, 51.934820, -4.179311) = 13 miles .. ;
h). Pen-crug-melyn to Foel Drygarn, (340 metres, 51.970606, -4.683437) = 21 miles .. .
I'm not suggesting that the people would have moved from one mountain top to the next, but they may have initially used the peaks as land marks. Moss would have grown on the north facing side of tree trunks, just as it does today, and they could have used this feature as a reasonably accurate compass, which would overcome the problem of mental maps. With the trackways becoming more established the navigation problem would disappear.
As your blog is world-wide it follows that many of the readers/contributors would have no knowledge of the topography of the land between Preseli and Salisbury Plain. Attached are two photos which may assist, both were taken from Hay Bluff (a) looking to the Malvern Hills and (b) looking towards Pen-y-Fan.
Comment: On looking at the "overland human transport" hypothesis (favoured by MPP and others) it's indisputable that people would have wandered about over considerable distances in the Neolithic. And yes, we can assume that they would have used landmarks and sightlines, as well as navigating by the sun, moon and stars. But I have particular problems relating to the nature of the terrain. As Aubrey Burl and others have pointed out, anybody proposing to carry one large stone (let alone 80) overland over a great distance would have to cope with what was essentialy a trackless jungle, in which long-distance sightlines would have been very difficult to follow, except maybe on the high ridges. Sorry Phil -- I don't buy it! (And by the way, in Wales there is moss everywhere, not just on the northern sides of trees....... not that people would have had any problem distinguishing north from south.)