Musketballs, Mortars and Matchlocks

What do you think of when you think of archaeology? For the majority of people the answer is simple- ‘musketballs’. If that wasn’t the first thing in your head, there’s no need to fret; ‘fragmented portion of a 17th century grenade’ is also a perfectly acceptable answer. Ok, none of the above is true. But for me it is objects such as these that make up my Day of Archaeology.

I work as Operations Manager for a commercial company, Headland Archaeology (Ireland) Ltd. The majority of my work involves overseeing all the projects we undertake and making sure they run smoothly, are carried out to a high standard and progress as efficiently as possible.  However, I also specialise in ‘Conflict Archaeology’, a field of study which explores evidence for the forms and effects of conflict on past populations. Today is a ‘Conflict Archaeology’ day.

The material I work with the most relates to conflict in 16th and 17th century Ireland. This was an exceptionally bloody period in Irish history. The Elizabethan Conquest of Ireland took place in the second half of the 16th century, while the 1640s witnessed eleven years of war, culminating in the Cromwellian intervention on the island. Later still the War of the Two Kings was fought between William III and James II’s forces. The conflict artefacts and conflict architecture left behind on sites from this period can tell us much about the personal experience of individuals during these troubled times. What was it like to be a soldier in one of these armies? How did they operate? What affect did the wars have on the civilian populace?

Today I am working on an assemblage of military artefacts from a Castle site which was besieged in 1653, when Parliamentarian forces bombarded the site and forced the Irish defenders’ surrender. Although there are some historical accounts of the siege, many details of the engagement remain unknown. This is where the artefacts come in. It becomes quickly apparent to me as I trawl through nearly 200 iron ball fragments that the castle was extremely heavily bombarded. The sheer number of fragments is unusual in Irish archaeology- it is the highest concentration of artillery projectiles from a conflict site I have yet come across in the country.

What can they tell us? They are all heavily damaged, with only one complete spherical ball surviving. This suggests that the projectiles shattered as they struck masonry, or split into deadly shrapnel as they exploded. Their form tells us that the Parliamentarians used at least two main types of projectile; solid iron balls and mortars. The solid shot was intended to break down the walls of the castle, while the mortars (hollow iron spheres filled with powder) would explode and fragment as they rained down on the defenders.

I am currently analysing the size of the fragments to try and tell what type of artillery piece fired them. Although most iron balls are today usually called ‘cannonballs’, in the 17th century a ‘Cannon’ was a specific type of gun which fired a particular size of ball. Many other types existed, with names like ‘Culverins’ ‘Sakers’ and ‘Falcons’. These fired different sizes of ball over varying distances. Identifying the type of gun can help us identify how far away the besiegers may have been from the castle, and also tell us how difficult it was to get them into position. For example, some of these guns required dozens of oxen to haul them around the countryside.

'17th century grenade and lead shot'

And what of the defenders? The majority survived this siege and were able to surrender, but the castle was destroyed in the bombardment. Among the military artefacts that relate to them are lead musketballs (also called lead shot) and weapon fragments recovered from the rubble. The size, shape and weight of the musketballs can tell us what types of gun they were used in, provide information about how they were manufactured and also suggest if they have been fired or not. The examples from this site appear unfired, so they may have been dropped or lost by the defenders. This site is unusual in that it has also produced part of the firing mechanisms from some of the defender’s weapons, most likely destroyed during the bombardment. These fragments are from matchlock muskets, a type of gun that used a lit piece of cord to fire the musketball.

When I have finished the technical analysis of the material (a process which will take a few days) it will be possible to build a picture of the siege. I will be addressing what types of artillery the Parliamentarians brought with them, how this was used and transported and where it might have been fired from. From the defenders viewpoint it should be possible to suggest how the bombardment was experienced by the men within the castle, as well as talk about how they were prepared to meet the onslaught. This is all in the future, however, and for now I am immersed in the technical analysis of each of the artefacts.

So, this is how I am spending my Day of Archaeology, 29th July 2011! Every object I am handling was deposited over a handful of days 358 years ago, in what must have been an extremely dramatic and traumatic event in the lives of all those who were present. For some these objects represent their final moments.  It is an honour and privilege to deal with these artefacts, as by doing so you are literally ‘touching history’; the results of the analysis itself helps bring this history to life. It is certainly one of the most fascinating ways to spend a day that I can think of!

Ancient concrete? Really?

Yes, really.  I first fell in love with old buildings in Pompeii, where I spent summers working as an excavator from 2002-2008. Every day it struck me that I was in a place that still looked and felt like a real city. To my mind, this was down to the fact that the buildings are still standing. After more than 2000 years. Someone did something very, very right when making those buildings and I want to know more.

For my D.Phil research, I have landed in an opportunity to study structures in Ostia, Italy, which is also a preserved city-sized site.  The structures I’m investigating are all brick and mortar masonry, with concrete filling up the center wall core. This is what Vitruvius called opus caementicium. To be honest, I’m most interested in the people who made it: the builders who developed this wonderful, magical material that is still performing successfully more than 2000 years after it was first installed. Where did they get their materials? Why were certain materials preferred over others? How were the materials processed and mixed together? How did builders’ choices affect the concrete and its performance? Were the same mix types used for both public and private structures? Why is this stuff still standing? These are the questions driving my research, and I am looking to answer them by investigating the material itself.

To give a quick overview, the mortar and concrete I am analyzing was made of lime, volcanic sand aggregate, and water. Sounds rather simple, however, the combination of materials they were using produced complex chemical reactions, known to modern concrete scientists as pozzolanic reactions, which resulted in a sophisticated, high quality material. My sample collection was collected from a series of structures in Ostia from the 2nd century CE, by which time – at least in Rome – concrete was well-developed and had been employed in large-scale Imperial building projects. My task now is to analyze the Ostian structures to determine how well-developed their concrete industry had become by that time. The benefit of a site like Ostia is that the ancient city is left largely in tact without modern development. This means that unlike in Rome, where centuries of modern development has destroyed all but the most protected monumental structures, it will be possible to evaluate the buildings within their original cultural context.

The analytical techniques employed for my research are borrowed from geology and concrete science, which makes this a truly interdisciplinary project. My samples are essentially synthetic composites of natural materials that can be investigated with traditional petrography. I’m using light microscopy of thin sections to identify and quantify the aggregate, to describe the cementitious matrix, and to identify any  obvious degradation features or alteration products. Today I’m working on point counting one of the samples, which is pretty straight forward. I move across the sample in 1 mm steps, and at each location I record what I see in the cross hairs of the eyepiece. Besides the obvious benefit of quantifying each of the different components, I’m also getting to the know the sample really well. As I go, I’m recording information about the state of degradation or alteration, the shape and fillings of any cracks or holes, particle size and shape, and any other details that may give me a clue about what the builders were doing when they made the concrete.

I am also using scanning electron microscopy (SEM) to collect high-resolution, high-magnification backscatter images of the samples. At this scale I can get a better look at the binder-aggregate interface to see how well-bonded these components are. It is also possible to see any microscopic cements that have formed in pores, cracks, and the vesicles of aggregate clasts that would otherwise not be visible. The SEM also detects the atomic weights of everything in the sample, which show up as differences in the greyscale colour of the image. It  also can calculate the chemical composition of the different components, so using a combination of chemical data and backscatter images, I can determine what types of cements have formed (strengthening) and how much leaching has occurred across the matrix (degradation). The ratio of calcium to silica is key in both cases.

X-ray diffraction is also on the menu, assuming I can find the funding to pay for it. This technique is incredibly useful for identifying the mineral assemblage in rocks and materials. In this case, I will use it to confirm the original petrographic identification of minerals in the aggregate and to find any other alteration minerals that could not be seen in thin section. The presence of certain minerals like gypsum or ettringite usually indicate alteration of the mortar itself, but minerals such as stratlingite and calcium-aluminum-silicate-hydrates suggest the mortar was rather well-formed in the first place.

So today, I’ll be giving an account of what it’s like for me in the lab. I realize that being stuck in the lab sounds like a death sentence to some people, but for me, it’s where the magic happens.