Last summer when it we had weeks of hot dry weather I noticed and published on this blog the discovery of some parchmarks in the south west corner of the Stonehenge outer sarsen circle - see http://www.sarsen.org/2013/07/partch-marks-at-stonehenge.html
This provided the first evidence (though not conclusive) for the existence of stoneholes, and hence, the stones 17 and 18.
The stoneholes for 20 and 19, as well as other recorded holes, showed up as parchmarks as well.
The top of Stone 19 still lies on the ground and I thought it would be interesting to compare it with the parchmark of its stonehole. And it is a fairly good fit for width, though of course the missing part of the stone may have been wider or narrower.
The parchmark from the south west.
The remains of stone 19 (stone to the right is a fallen lintel) the break would be about half way down the stone, the bottom half is missing.
The top of Stone 19
One oft the tenons, much eroded, on the top of stone 19.
(click any to embiggen)