What is this mystery find ?

[KidKruger]

About 8yrs ago I posted on EDF some pics of something I had found in the Thames, hoping for an answer as to it's purpose and age.

I can't find that post now, so now I'm posting new photos with a question to all - what is this and how old ?

Info:

- made of stone by looks of it

- 10" diameter

- 6" deep

- the square hole in centre is 3 1/4"

[KidKruger]

More pics.

[malumbu]

Looks like a small grinding stone, for a small windmill or watermill

[bettyorange]

Yes definately a millstone.

[Blah Blah]

It is too small for a millstone. My guess would be a grinding stone to sharpen tools.

[diable rouge]

Don't millstones need a flat, smooth surface in order to grind properly?...https://www.dandelionstonetroughs.co.uk/millstones-for-sale/

ETA: Are the grooves helical like a screw? If so could be a rope mooring of some kind.

[Blah Blah]

They do and they are usually far bigger than that. The other thing that occurred to me, looking at the grooves, is as some part of a pulley system, with the rope gripping in those side grooves. The beam going through it then in turn, turns something else.

[KidKruger]

When I found it, with one edge sticking out of the mud, I thought it was the edge of a large stoneware jar.

As I dug deeper I realised it was something else and the grooves around the side left me pondering.

I did speculate whether it was some kind of maritime mooring block whereby it slotted over an upright wooden post and rested on the jetty, while ropes were tied around it and eroded the sides in that uneven way (no, DR, there's no helical groove).

I then wondered if it could have been part of a pulley system, but why use stone as a material for a pulley I thought ?

After that, I figured it may be the base of an ancient stone column, where horses/cattle had for an extended period of time been tethered and caused the erosion on the sides.

[Spartacus]

Half a stone age jammy dodger

Obvious really

[KidKruger]

So I found out what this is by talking with a Thames finds specialist who advised me as follows.

It's a late medieval grindstone. That is, a grindstone for blades such as knifes, axes, swords. It would have been hung on a square timber section which was attached to a turning apparatus to be spun by hand, probably a large handle to the side. It's fine-grain stone, typical of grindstones used then.

How and why it ended-up in the Thames is a point of intrigue, possibly it fell from a jetty or boat, being probably too heavy to be washed around by the river so being found where it fell, in the mud.

Glad to have got this resolved.

I was watching a YT clip by this chap and, during his short about his 10x best Thames stone finds, he holds-up a fragment (about a quarter) of a grindstone similar to mine. I then realised what I probably had found. So I contacted him and he confirmed the find.

I'll talk to MoL and see if they want it to display as part of the Thames finds section, I'll construct the wooden apparatus if they want.

I see no photos or diagrams of grindstones with same features as the one I found, so I'll take the advice for now as it's the best I've had, but I've a nagging doubt it's not the entire story - until I learn more.

[ponderwoman]

It would work for sharpening gouge chisels on the rounded ridges. All the many blade sharpening grindstones I have seen retain a clear 90 degree edge, not the rounded one yours has. I would have thought that it had pulley grooves but the stone looks like it would abrade rope rather than the stone becoming polished by use.

[KidKruger]

Yeah I pondered this, ponderwoman, good point.

I noticed 90 degree angles on other grinding stones on t?internet, too.

I?ll ask the expert I was communicating with earlier.

Perhaps there?s more yet to this story.

[DulwichFox]

I am interested to know where on the Thames it was found. ?

North or South Bank. I believe it has something to do with business activity,

Part of Lifting gear.. Barge loading... Brewery ... Flour Mills .... ??

I Believe it is old.

Foxy

[diable rouge]

Googling 'ancient stone pulley' doesn't throw up much beyond what the Egyptians used to build the pyramids, which makes sense with the loads they were shifting. For less strenuous lifting work it does seem a lot of effort to make a pulley from a lump of stone when it would've been much easier to do it in timber, which are far more common. I'm starting to think it's more likely to be the base of a decorative column...

[DulwichFox]

The Square hole suggests some sort of drive shaft. Probably wooden.

Did the shaft drive the stone or did the stone drive the shaft via pulleys. ??

The stone is very small ?

Food for thought.

Foxy

[KidKruger]

Foxy,

Found in the Thames at Rotherhithe, 100m West of the Surrey Docks Farm site.

DulwichFox Wrote:

-------------------------------------------------------

> I am interested to know where on the Thames it was

> found. ?

>

> North or South Bank. I believe it has something

> to do with business activity,

>

> Part of Lifting gear.. Barge loading... Brewery

> ... Flour Mills .... ??

>

> I Believe it is old.

>

> Foxy

[diable rouge]

How bridges were built in Central Europe during the Middle Ages...https://twitter.com/KiwiEV/status/1316493212605911040

[KidKruger]

That's fascinating. I was waiting for the stone column or something to appear and solve this mystery tho !!

[Earl Aelfheah]

Great find.

[diable rouge]

Spoiler alert! :)...

[KidKruger]

I have contacted the expert again to ask specifically about the grooves (as pointed out by blahblah and ponderwoman) in the edge of the grind stone not resembling other (what seem to be) traditional grindstones used for sharpening blades.

The fact that it's not a stroll finding the answer on the www I find interesting.

Thanks for all replies so far.

[ianr]

I did a lot of web searching at the time as well. I eventually came to the conclusion, which I still hold to, that those grooves/striations most closely resembled images of natural abrasion and erosion by wind or water, as in these examples:

https://thumbs.dreamstime.com/z/weathered-rocks-beach-large-wind-water-yellow-sand-pacific-ocean-surf-51315541.jpg

https://image.slidesharecdn.com/weatheringanderosion-easier-130403080226-phpapp01/95/weathering-erosion-and-deposition3rd4th-grade-teach-1-638.jpg

https://image.slidesharecdn.com/weatheringanderosion-easier-130403080226-phpapp01/95/weathering-erosion-and-deposition3rd4th-grade-teach-24-638.jpg

http://www.passmyexams.co.uk/GCSE/physics/images/weathering_wind.jpg

The Thames is tidal where they were recovered, in't it, so it's fairly easy to imagine gradual wear from particles on or streaming over the river bed. But what did your expert say?

[17/8/21 Nailed it. See attached.]