Forms of leather

There are a number of processes whereby the skin of a dead animal can be formed into a flexible, strong material generally called leather.
Vegetable-tanned leather is tanned using tannin and further ingredients found in vegetable stuff, tree bark, and other such sources. It is flexible and brown in color, with the exact shade depending on the mix of chemicals and the color of the flesh. Vegetable-tanned fur is not stable in water; it tends to discolor, and if left to soak and then dry it will shrink and become less supple and harder. In hot water, it will shrivel drastically and plasticize, becoming rigid and ultimately becoming brittle.
Alum-tanned leather is tanned with aluminium salts assorted with a variety of binders and protein sources, such as flour, egg yolk, etc. Purists argue that alum-tanned leather is technically "tawed" and not tanned, as the resulting stuff will rot in water. Very light shades of leather are potential using this process, but the resultant material is not as supple as vegetable-tanned leather.

The bluestones
Roger Mercer has observed that the bluestones are incongruously finely worked and has suggested that they were transferred to Salisbury Plain from an as yet unlocated earlier monument in Pembrokeshire. J. F. S. Stone felt that a Bluestone monument had earlier stood near the nearby Stonehenge cursus and been moved to their current site from there. If Mercer's theory is correct then the bluestones may have been transplanted to cement an alliance or display superiority over a conquered enemy although this can only be speculation. Oval shaped settings of bluestones similar to those at Stonehenge 3iv are also known at the sites of Bedd Arthur in the Preseli Hills and at Skomer Island off the southwest coast of Pembrokeshire. Some archaeologists have suggested that the igneous bluestones and sedimentary sarsens had some symbolism, of a union between two cultures from different landscapes and therefore from different backgrounds.Recent analysis of contemporary burials found nearby known as the Boscombe Bowmen, has indicated that at least some of the individuals associated with Stonehenge 3 came either from Wales or from some other European area of ancient rocks. Petrological analysis of the stones themselves has verified that they could only have come from the Preseli Hills and it is tempting to connect the two.The main source of the bluestones is now identified with the dolerite outcrops around Carn Menyn although work led by Olwen Williams-Thorpe of the Open University has shown that other bluestones came from outcrops up to 10 km away.Aubrey Burl and a number of geologists and geomorphologists contend that the bluestones were not transported by human agency at all and were instead brought by glaciers at least part of the way from Wales during the Pleistocene. There is good geological and glaciological evidence that glacier ice did move across Preseli and did reach the Somerset coast. However, it is uncertain that it reached Salisbury Plain, and no further specimens of the unusual dolerite stone have so far been found in the vicinity. One current view is that glacier ice transported the stones as far as Somerset, and that they were collected from there by the builders of Stonehenge.