Sunday, 3 March 2013

A Bluestone Problem Solved

From The Laser Scan report on Stonehenge we get this table of the visible Bluestones:


Stone number                               Vol (m3)           Weight (Tonnes)
310.682.04
32‡0.381.14
330.170.51
340.110.33
35a‡0.00070.002
35b‡0.0030.01
36‡0.090.27
370.270.81
38
39‡0.160.48
40
41‡0.240.72
42‡0.10.3
43
44
45‡0.140.42
46†0.140.34
470.421.26
48‡†0.0660.16
490.371.11
610.320.961
620.411.23
630.41.2
64
65
67‡0.531.59
680.712.13
690.722.16
700.411.23
72*0.511.53


The weights and volumes are of the visible portion so we can guesstimate that there is a third or so more of the stone underground. To be generous to allow for the above portion of the stones being eroded let us double the weights. The heaviest stone is at most four tonnes, most are much less.

Atkinson in his book Stonehenge (1956) p99 writes that the stones weighed "up to four tons apiece". But somehow the idea that the stones weighed five to eight tonnes became common. It is importnat because moving a two, three or even four tonne rock is a very different order of difficulty to moving an eight tonne one.


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