I’ve always had a love of history and archaeology, but only ever dabbled, mostly during house renovations in the UK and Australia, but have always worried about not doing it properly. While on a trip to the UK in August 2015, I made the effort to learn a bit more of how to practice the discipline of archaeology while being an amateur, and found it’s not that hard to really do things properly without risking permanently damaging or losing vital information or physical evidence.
My mum had spotted an advert in the local rag for an annual open “Pub Dig” by Liss Archaeology which was fortunatley a couple of days after we arrived had got over our jet lag – and on a beautiful summer’s day. So we signed the health & safety forms and started to get trained by the friendly local group who’d been asked to investigate a C17th pub rumoured to have once harboured a couple of sailor-murdering ruffians who were promply hung and left in gibbets on Box Hill for the crows.
Helen, who studies weaving in iron-age roundhouses for her PhD, at Butser Ancient Farm practical archaeology research site, showed us how to clean up the sides of a trench for recording, and how to slowly lower the floor level to a specified horizon.
Before we knew it, we were uncovering pot sherds from Saxon and iron-age! I honestly do know how fortunate we were to have this amazing experience, as finding anything Saxon other than a smudge in the ground, or relics from the even more ancient prehistoric bronze/iron age is rare even for those who dig every day… we were truly stunned.
Ever since I’ve known Gen, she’s wanted to find clay-pipe. It’s become a bit of a mantra while we’ve been renovating our 1870’s Sydney cottage – everything but clay pipe! Coins, letters, lace-gloves, tools, marbles, bullets, newspaper, books, shoes – all from the 1850’s onwards but not a pipe in sight. When we visit The Rock’s museums, we smugly point at all the various items on display and say “Got one, got two, got one, got three…” but when it comes to clay pipe, there’s just cicadas.
As we first walked up to the Liss site director, a guy came over and said “Hey I just found this clay pipe in the spoil heap!” and Gen’s eye’s popped out. They had found a fair few peices, including two bowls which were identifiable by their dimensions, and the floral icon on the side of the base. Interestingly, we “redeposited” all the broken stems back into the trench while back-filling later, along with all the other non-essential items.
They were a lovely team, Chris the pottery expert, Dave “the boss”, Graham “the seive” and others who’s names I think I also reburied. All very welcoming and patiently forgiving of a noob like myself who kept handing them stones and even leaves excitedly asking “what’s this!”.
So full of renewed vigour we head off back to my parents “new” house, with thoughts of what we might be able to find there. My folks move every 2yrs on average (over a 50yr sample – a very reliable statistic), so seeing as I haven’t visited for some 28months – there’s fresh turf to investigate!
Last time, it was a relatively new house (1950’s) but still on the grounds, there was a 1920’s “midden” or dump, which contained some classic items such as glass jars, medicine bottles, enamel-ware etc.
Previously, they lived in a “church cottage” built around a Tudor chapel, where I first bought “them” a metal-detector and found the remains of a cow-shed which had wartime relics deposited including a home-guard helmet. I also found Tudor green-glaze pottery and slag.
This time it’s again a 1930’s house, but built on older land in a historic area. So what will we find?
First off, I dusted off the metal detector, but after “doing it properly” with the team from Liss, I didn’t feel so inclined to rush in digging up stuff randomly. I did a couple of spot digs, and found a plated metal star, possibly from a chandelier. I also found an iron ring, which normally I’d ignore using the detector’s iron-discriminator, but it seems that a ring still triggers the detector when face-on possibly due to strange currents or EM signals in the ring itself. Well lucky for that – because as soon as I had turfed a foot square section to look for the beeping item – a peice of clay-pipe just popped out! Then another! Gen was beside herself.
So I thought about it, and closed up the turf without further disturbance. I want to do this one as properly as possible without a degree in archaeology, but armed with the power of the Internet and 6 weeks of working/holiday to allow me to take my time.
On a side trip to Oxford, to stay at one of the colleges with Gen’s professor associates, we stopped off near Stonehenge at a white-horse carved in to the hillside. As we were circling the iron-age hill fort, I said to Gen “I’ll just have a look at what the moles have brought up” – a sneaky way to find items without digging yourself. And sure enough – sticking out of the very first molehill I looked at: clay pipe. Gen just couldn’t beleive it!
Looking around a few more, we found various items, including more modern ceramics, burned ore and – I think – Saxon pottery. Of course this was an extremely sensitive and ancient site, so we barely touched anything, taking some photos and pushing the items back into the molehills, safely out of sight but only millimetres from whence they naturally emerged.
I woke up the next day back at my parents with one word in my mind: resistivity. The guys from Liss had been using a resistivity meter for their geophysics because magnetic would have been pointless in a pub garden which had been used as a building site, allotment, carpark etc. for 1,000 years and radar is beyond the budget of a local volunteer team. They had found some dark patches where chickens had fertilised the ground for donkeys years, and the resulting foliage was holding more water. They found an exciting looking circle but it turned out to be a featureless sand pit. They also found a roman-villa looking set of stripes, which turned out to be a house-less Edwardian garden.
As I woke up I remembered “Scruffy” Evans teaching me about resistivity at school, and I suddenly decided I could build my own geophys survey device! I had the time, the patience, and the tools. The Internet had the knowledge, as unfortunately (sorry Scruffy) I had briefly archived the definition of resistivity.
In my Dad’s garage I found everything needed to build a simple resistivity meter!
- a broom stick and dowel
- junction terminals
- some long brass screws
- some very long steel screws (v2!)
- velcro, cable ties
I made a simple H frame by doweling the rods into the broomstick, gluing and screwing with brass screws, Then set the long screws poking through downwards at 1m spacing. (It’s important to use standard spacing as there are tables developed over years to help interpret the results.)
The probe screws were simply connected to an Ohm-meter (a multi-meter) with some old mains wire I found. I also ground off the tips of the screw threads with a bench grinder, to make clean points.
That’s it for v1! (This is super-simple-basic, it’s not even the Wenner model – missing the middle voltmeter. I’ve got plans for v2,3,4… but I’m just really interested to see just how simple you can make a meter, and what sort of results you practically get.)
Then I “set out” the garden. I chose a good reference point for 0,0 which was in line with the corner of the house – something future people could replicate. I measured out 1m intervals in x,y direction and used string-line with 20cm and 1m markings as a guide.
First I tried a couple of runs of 12m, probing at 20cm intervals and recording the resistance on paper. After a while I found that the 3″ brass screws weren’t quite long enough to reliably penetrate the soil through the bouncy grass, so I removed them and used some 6″ steel screws. Brass would be better as it won’t corrode, but this is only a 6-week project.
Interestingly the next few runs gave significantly different results – lower readings by about 30%.
So of course I wanted to visualise the readings, but luckily being a programmer by trade, I was able to write my own custom software to display the results. I could probably have just used Excel/Google charts, but I do plan to take this further, so I invested a bit more time in building a mini framework to allow, for example, to add in image processing such as gaussian smoothing or the aforementioned depth charts (which I don’t understand yet!). I’ve recently been experimenting with a little Backbone+Bootstrap+Sass+Gulp setup, so it only took an hour or two to invest in making a basic Canvas rendering application with a decent model/view architecture (rather than just hacking some JS mudball).
I have to say seeing the first tantalising pixels was pretty exiting…
It was drizzling outside, and so I made the excuse of coming back in after each couple of runs to “dry off” and type in the 60 figures just recorded on a wet peice of paper pegged to the device.
As time went by, I could see diagonal lines and probably some other pareidolia so needed to get rid of the noise.
I rememberd a few bits from my AI degree computer vision course so I knocked up a simple Gaussian filter. The results were pretty good!
There has been lots of speculation about mazes, gardens, diamond-shaped cattle pens or just plain sewers. I guess we won’t know until we put a test pit in across one of the more prominent lines.
I must say, I’m pretty impressed so far with the results acheived “for free” with just a multimeter and a broomstick. I think this might be a good template for a project any kid could do in their garden in a weekend, so I will try to write up the “blueprints” and open-source the software.
Tomorrow I hope to do either a test pit, more resistivity at the darker area at the top, or the various metal detector points I’ve been ignoring. Also a friend of my folks apparently has a roman road under their house! But hold on… there’s plenty of exciting opportunities here – but I’m determined to proceed carefully and to collected and document the contextual information for future generations.