Tag Archives: Mala

February fun

Partly as a training exercise for UCL students, and partly just to extend our surveys at Verulamium, members of CAGG were out in Verulamium Park and Abbey Orchard last Thursday and Friday.

The magnetometer was out in Abbey Orchard on Thursday in the hopes of completing that small area.  Unfortunately, I think it is jinxed.  On Thursday we had battery problems, and on Friday the odometer refused to work properly.  The sum total of a day and a half’s work?  Two partial grid squares…  Oh well, just chalk that one up to experience.  Here is the image of the slightly extended area, such as it is.

The Abbey Orchard survey.

The Abbey Orchard survey.

Having given-up in the mag, Jim West, Pauline Hey and I decided to use the Earth Resistance meter on Friday afternoon.  I had singled out an area where there is a clear building in the mag data, but some ferrous noise masked the western end of the building.  The weather was glorious for a mid-February day.

The Earth Resistance survey underway.

The Earth Resistance survey underway.

We managed four grid squares at the usual 0.5m spacing, not too bad for one afternoon’s work. As you can see in the next image, the mag survey shows a lovely building as white lines representing low magnetism.

The mag results in the area of the Earth Resistance survey.

The mag results in the area of the Earth Resistance survey.

The wide dark line coming from the SW corner is the ‘1955 ditch’, the first century boundary of the town first excavated by Frere in 1955.  The two parallel lighter lines which run just to the north of the building are part of a road.

Unfortunately, the Earth Resistance survey showed nothing of the building at all.

The Earth Resistance survey results.

The Earth Resistance survey results.

It shows the edge of the road beautifully, and a high-resistance feature parallel to the 1955 ditch.  Even the ditch itself shows as a wide band of low resistance.  Of the building, however, nothing!  It may be simply that the soil is so wet at the moment there is no contrast between the building and the surrounding soil matrix.  Alternatively, the building may have been robbed out.  We will have to run the GPR over it one day.

Unlike last November, the GPR suffered no glitches, and Mike Smith, John Dent and Graeme Spurway completed an area 160m by 40.  Added to the same sized area completed in November, we now have a nice block of GPR data 160m by 80m to look at.

The data were sliced using Larry Conyer’s system in 3ns slices.  I’ll go through these from the top down.  There are three areas of GPR survey shown.  The top half of the large block is the latest survey, the bottom half that undertaken last November.  The detached block to the west was undertaken by Ralph Potter in 2014.  Remember that this is a rather crude “mash-up” in Google Earth so the edges do not match very well.  As always the GPR data are deserving of a much more detailed analysis.

GPR slice 3, 10.5 to 13.5ns.

GPR slice 3, 10.5 to 13.5ns.

Slice 3 (above) mainly shows modern features surviving in the topsoil, especially broad cultivation marks running NNW–SSE across this field.  There are some hints of the archaeology just starting to show through.

GPR slice 4, 13.5 to 16.5ns.

GPR slice 4, 13.5 to 16.5ns.

Slice 4 clearly shows the upper levels of the archaeology.  Watling Street, which is running roughly north-south in the eastern half of the main area, has a big hole in it.  It has been severely robbed for building stone.  There is a minor road running SW-NE with a square building alongside it to the north with a small room on the western wall and what looks like a courtyard on the eastern side.

GPR slice 5, 16.5 to 19.5ns.

GPR slice 5, 16.5 to 19.5ns.

The main addition in slice 5 is the complex of buildings in the NW corner of the main area. These are probably associated with the pottery kiln which we have just clipped (the feature that looks like Mickey Mouse’s ears in the underlying mag data).

GPR slice 6, 19.5 to 22.5ns.

GPR slice 6, 19.5 to 22.5ns.

In slice 6, the spur road is clearer, especially near to Watling Street.  It looks as though there is a shallow valley running parallel to Watling Street which is now filled with a greater depth of topsoil which means that the archaeology does not show until the deeper slices.  It is also noticeable that the centre of Watling Street has fewer reflections than in the upper slices.  I guess that we are getting below the surface of the road, and the reflections either side of the road may be the ditches that Wheeler found filled with rubble.  The building complex just to the north of the spur road has hints of two more small buildings.

GPR slice 7, 22.5 to 25.5ns.

GPR slice 7, 22.5 to 25.5ns.

In this final slice we can see the two small buildings north of the spur road in more detail. There is also a long linear feature running N-S between Watling Street and the modern path.  It looks like a modern utility to me, but there isn’t one indicated on the map I have been given.

The GPR results are excellent, and it will be worth continuing to expand this area.

I’ve had a busy time speaking to various groups about CAGG’s work recently.  One of the lectures was as part of the Society of Antiquaries public engagement lecture series held on a Tuesday lunchtime once a month.  They video the talks and put them online, so if you would like to hear me talking about Verulamium once more, here is the link.

As always, many thanks to Ruth Halliwell, Peter Alley, Jim West, Mike Smith, Pauline Hey, John Dent,  and Graeme Spurway, as well as my students from UCL, for turning out in mid-February, although we were extremely lucky with the weather,

 

Bring me sunshine, bring me smiles…

Magging (c) Mike Smith 2015.

Magging (c) Mike Smith 2015.

For a change, or so it seems, it didn’t rain.  It got very threatening at the end of the day so we were pretty efficient packing up, but on the whole it was a lovely day with white fluffy clouds, We were a slightly smaller team than usual, but we still managed to run the mag and the GPR today.

Following yesterdays problems with the mag, Ellen implemented a high-tech solution…

The hi-tech solution.

The hi-tech solution.

The flowerpot came from our garden but sadly Homebase didn’t stock duct tape so we had to make do with “duck” tape.  What do ducks do with tape, I wonder?  When the season is over I think the machine is going for a service.

The mag started by re-doing one of yesterday’s dodgy squares, then complete the transect with its final partial, before starting the next transect.  Here is the overall view.

The mag survey after day 16.

The mag survey after day 16.

Sadly, I don’t think we’ll get the whole next transect done in the next three days.  The area we did today is an interesting contrast to earlier days.

The area surveyed on day 16.

The area surveyed on day 16.

There are quite a few pits, and a ditch which seems to continue the line of pits seen yesterday to the WSW of the “uber magnetic building”.  One of tomorrow’s grid squares should show us how this new ditch and the “sinuous ditch” meet.  No sign of the 1955 ditch’s northern arm yet, however.

Mike Langton, of Mala, kindly processed one block of GPR data — that surveyed on day 12 — for us using Reflex-W.  The results are very good. I have (a) a lot to learn and (b) a lot to do!

Time-slices of the dat 12 data by Mike Langton.

Time-slices of the dat 12 data by Mike Langton.

The eight slices start at 10ns and are 2ns thick.

Mike and I completed a grid square with the GPR in the morning, tidying up the block of grid squares so far surveyed.  Unfortunately, there doesn’t appear to be very much in it.

The centre block is the data collected on days 15 and 16.

The centre block is the data collected on days 15 and 16.

The same area without the GPR data for comparison.

The same area without the GPR data for comparison.

I decided that I couldn’t wait a year to find out more about the “uber magnetic” building, especially after the repeated failures of the res meter on that area.  Mike and Julia valiant struggled up and down the slope, occasionally assisted by myself.  Surprisingly, given the strength of the magnetic signal, the GPR showed very little apart from one corner.

GPR results over the "uber magnetic" building.

GPR results over the “uber magnetic” building.

The same area as the previous image for comparison.

The same area as the previous image for comparison.

It seems unlikely that a building like a bath house would show so poorly in the GPR data and so it seems more likely we are dealing with a burnt down timber structure.

We are on the last leg of this year’s survey.  Despite hiccups, rain and technical failures we already have some stunning results.  Let’s hope for a few more in the last days.

Many thanks to everyone who turned up today and did such sterling work.