Saturday, March 31, 2007

..When ye shall take your ass at Port Jaffa...

A 15th c. guide to pilgrimage travel details.

Oh Brave New World...

..that has website-trampling dinosaurs in it.

Also wasps, meteor showers, attacking martians and the cursor-directed hand of a vengeful God.

Not to mention marching medievalists.

How Many Sunnis?

A recent poll carried out in Iraq for ABC News, USA Today, the BBC and ARD German TV had one result that seems to have gotten less media coverage than it deserves. Conventional wisdom has been that Sunni Arabs represent something like 12-22% of the population of Iraq.

Recent survey data, including this poll, have had different results. This survey found 47 percent Shiite Arabs, 35 percent Sunni Arabs, 15 percent Kurds and three percent others.

D3 Systems reports that in its previous surveys it has seen Shiite Arabs in a range from the high 40s to low 50s, and Sunni Arabs in a range from the high 20s to mid-30s. The 35 percent Sunni Arab estimate in this poll is at the high end of its previous data, but within that range. This poll had more sampling points than any previous individual national study in Iraq by D3/KARL

Another large poll, carried by ORB gave similar results: 32% Sunni Arab, 42% Shiite Arab, and another 9% Arabs who didn’t identify their sect. It turns out that the lower estimates, while widely quoted, don’t seem to have a lot of sourced evidence behind them.

As far as we have been able to ascertain there is no official Iraqi estimate of the country's Sunni vs. Shiite Arab populations, and no single authoritative source of empirical data on the subject.

Needless to say, if these numbers are correct and previous Western estimates wrong, they should radically alter our view of likely outcomes in a sectarian conflict in Iraq. If Sunni Arabs there have a population that is 75% of the Shiite population rather than 35%, the decision of insurgents to provoke sectarian conflict begins to seem much more rational.

Tuesday, March 27, 2007

Global Warming: A Modest Proposal

I believe that global warming is a real problem, and the result, even if non-catastrophic, of continuing the status quo will be billions of dollars of net economic damage over the next century. A good first step would be a tax on carbon emissions.

Economist William D. Nordhaus has estimated that an optimal carbon tax might start at $16 a ton (less than five cents a gallon of gasoline) and rise over time. Such a policy would be a good first step, but would still leave some countries as net losers. Nordhaus argues convincingly that a tax that reduced climate change to zero would cost more than the economic benefits it provided. Even this was not the case, imposing such a high tax would be politically impossible. Countries that were already hot, highly dependent on agriculture, low lying, and relatively low per capita producers of greenhouse gasses would be net losers, and many of these countries are already poor.

What can be done for them? One option might be for countries that are net beneficiaries of the production of greenhouse gasses to send the governments of the disadvantaged countries a check. This may not always be the best option. Here are some other ideas:

Cut or reduce tariffs on their products
Stop subsidizing our agricultural production so that it’s harder for them to compete with it.

Farmers are a powerful and concentrated interest that will fight a simple elimination of these benefits tooth and nail, so a third step will probably be required as a matter of practical politics: replace current agricultural subsidies and protective tariffs with payments simply for keeping arable land green.

This is a change that makes some sense on its own merits. Having green fields to look at rather than strip malls is arguably a public good that the rest of us should be willing to subsidize. Less so low cost corn syrup.

Sunday, March 25, 2007

A False Argument Against Reasonable Carbon Taxes

In his blog, David Friedman writes:

In earlier posts I argued that global warming is probably real, probably anthropogenic, and will probably impose real but not catastrophic, costs. This raises an obvious question: What, if anything, should we do about it?

If I were dictator of the world, the answer would be fairly obvious. Impose a tax on activities that create greenhouse gases designed to reflect the marginal cost they create. That's the standard economic solution, due to Pigou, for problems of negative externalities. Since the tax brings in additional revenue, combine it with a corresponding reduction in whatever taxes currently have the largest adverse effects.

I do not, in fact, support such carbon taxes. The reason is that I do not believe that, if imposed, they would fit the pattern described above.

To begin with, they would not be based on a realistic estimate of the marginal costs; insofar as they would be based on anything, judging by the ongoing arguments over Kyoto and similar proposals, they would be based on some target level of emissions. If, as seems likely, the level of taxes needed to substantially slow global warming was much higher than the marginal damage done, the result would be to buy lower temperature at a price much higher than it was worth, making the net situation worse, not better.

But this misrepresents the actual political process. Kyoto was expressed as target levels of emissions, but these targets emerged from a tension between the desire to mitigate global warming, or at least be seen as trying to do so, and the desire of the countries involved to keep costs to their citizens as low as possible. The targets of Kyoto may have been higher than marginal costs might dictate, but they rarely resulted in legislation at a national level that was as draconian as the targets would actually require. The actual level of expense US taxpayers seem to be willing to impose on themselves to reduce carbon emissions is closer to the Pigouvian or Lomborgian level than the harmful level that Friedman fears. It present, the level is closer still to zero.

I offer as further evidence the arguments I have been having over at Brian's "Backseat Driving" blog with people who are absolutely convinced that global warming would have catastrophic consequences but curiously unwilling to support that conviction with anything more than handwaving arguments. Judging by casual observation, they are the norm, not the outliers, of their movement.

That movement, however, does not occupy the center of gravity of the US political marketplace. They are no more representative of the median voter or legislator than do the people that claim for various reasons that no meaningful government action at all should be taken to address global warming.

Furthermore, I think it unlikely that income from carbon taxes would be used to reduce other taxes. The clear evidence here is the repeated pattern with regard to wars. New taxes are introduced as an emergency measure for a war, retained long after the war is over; there is always some politically profitable way to spend the money. In the case of carbon taxes, I am confident that they would be used as an additional source of revenue, perhaps with the argument that the money was needed to ameliorate the effects of whatever global warming continued to occur.

On the other hand, lower taxes are popular. Reagan didn’t wait for the end of the Cold War to cut taxes, nor did Bush wait until the end of his wars to do so. There are always politically profitable ways to cut taxes, even if you have to pass the bill on to future taxpayers to do it.

Finally, I suspect that widespread acceptance of the catastrophist view of global warming would result in quite a lot more than carbon taxes. It would provide a new justification for politically motivated interferences in a wide range of human activities. Anyone who questioned such policies would be labelled a denialist, accused of wanting Bangladeshis to drown and African children to starve. Again, look at the ongoing exchanges on Brian's blog.

Hence I conclude that serious efforts to combat global warming would have large costs, costs justified only if there were good reason to be confident that not taking such efforts would have catastrophic effects.

As I understand it, Friedman is arguing that a Pigouvian level of carbon tax: perhaps $10-20 a ton based on plausible discount rates, would be a good thing. However, he would not want to do this good thing, because it would enable catastrophists to sweep in and enact far more draconian levies, as well as giving them license to send the Energy Greenshirts in the middle of the night to tear our incandescent light bulbs from our cold dead hands.

He seems to be arguing that we should therefore prefer the status quo to a Pigouvian carbon tax, even though the result would be significantly greater economic damage to Bangladeshis and Africans than might be expected with a reasonable carbon tax. Given the level of poverty in those places, I would expect the economic damage to result in a higher death rate. I wouldn’t want to accuse David Friedman of wanting this outcome for Africans and Bangladeshis, but it seems to be the logical result of his argument.

Sunday, March 04, 2007

Length of Medieval Lances

How long were the heavy lances used by medieval men-at-arms on horseback in the 14th and 15th century? Contemporary artwork provides some evidence, when the composition suggests that there was no need to distort the size of the lance to fit it into the picture. Skeletal evidence gives an average height for medieval English males at 5’ 7.5”. It seems likely that the upper classes, with better than average nutrition in childhood, were about an inch taller.

Scaling to an average height for a man at arms of about 5’ 8”, the lances in these paintings would have the following approximate lengths:

Lancelot du Lac MS, ca 1380 9.2-9.4'
Altichiero, Saint George Chapel, Legend of Saint George 1378-84 9.5’
Roger Van der Weyden, Saint George and the Dragon c 1432 11.5’
Paolo Uccello, the Rout of San Romano c. 1450 11.5’

One further piece of evidence: Giovanni dall’Agochie, writing in 1572, recommends a lance length of ten feet.

It would appear that lances became significantly heavier, both thicker and longer, after lance rests came into common use, beginning around the end of the 14th century.

Some additional information on 16th c. lance dimensions is available here.

Impact Energy of Arrows at Different Ranges

An appendix in The Great War Bow by Mathew Strickland and Robert Hardy contains some interesting data on the impact energy of arrows at various ranges. For a 95.9 gm (3.3 oz) arrow with a long bodkin point from a bow of 150 lbs draw, the results were as follows, based on measured initial velocity and recorded range and drag coefficient estimated based on the observed values for initial velocity, range and launch angle. The initial kinetic energy was 134 joules.

Range(m) Impact Energy(J)

50m 115J
100m 98J
150m 85J
180m 80J
200m 78J

Friday, March 02, 2007

My Harness: Rear View

The design of the rear of this body armor is based on a misericord in Lincoln cathedral that shows a knight tumbling from his horse.

Thursday, March 01, 2007

Thrusting Against Visors

Accounts of deeds of arms in the 15th century frequently mention thrusting against visors. It is very difficult to achieve significant penetration of a steel or iron steel plate 1.5 mm or more in thickness with even a two handed thrust, and most visors seem to have been at least that thick. What were these attackers trying to accomplish?

Visors present a number of vulnerabilities. While eyeslots were usually a very small target on a medieval helmet, an accurate or lucky thrust could penetrate them, with unpleasant consequences. Chastelain reports that when Jacques Lalaing fought Diego de Guzman at Valladolid, Lalaing “turned the lower point of his axe, and struck three blows, one after the other, within the eyeslots of Diego, in this way: he wounded him in three places in the face…the first stroke on the left eyebrow, the next on the bottom of the forehead on the right side, and the third beneath the right eye….”

Given the number of blows that penetrated Guzman’s eyeslot without hitting an eye, I suspect that Lalaing was deliberately choosing angles of attack that were likely to produce a bloody wound, but unlikely to blind his companion.

And having achieved the difficult task of penetrating his opponent's eyeslot, it's possible that his point never left it for the next two blows, instead pulling back only far enough to shift to a different aim point on Guzman's face.

Also, positive mechanical catches to keep visors closed seem to have been a relatively late development: I know of no clear examples before around the middle of the 15th century. Earlier, visors seem to have depended entirely on the friction of their pivots to keep closed, and one or more vigorous upward thrusts could drive a visor open, leaving the face vulnerable to a following thrust. Monstrelet records that when Poton de Saintrailles fought Lyonnel de Wandonne at Arras in 1423: “watching his opportunity, he closed with Lyonnel and struck him many blows with the point of his axe under the visor of his basinet so that he raised the visor, and the face of Lyonnel was clearly seen.”

Finally, the numerous breaths that perforated the visor of the typical helmet intended for foot combat presented another point of vulnerability. In at least one case, the chronicler suggests that a very acute point might actually slip through the breaths far enough to injure the face. De la Marche reports that when Bernard de Bearn, Bastard de Foix fought the Lord of Haubourdin in a continuation of the Pas de la Pelerin of 1446, Bernard bore an axe with a lower spike that was “long and delicate, fashioned so that it might easily enter the holes of a basinet, and long enough to do great damage to the face of his companion”. This seems to have been unusual enough to draw comment. A very slender spike would be vulnerable to breakage. Probably Habourdin had visor holes that were small enough to exclude the typical robust pollaxe thrusting point, but vulnerable to the unusually acute point chosen by Bernard de Bearn. Habourdin seems to have been distinctly miffed by Bernard’s tactic. “When he was advised of the subtlety of the said axe, he said that he didn’t want to make his companion take pains to pierce the visor of his basinet. He quickly had his detached and entirely put aside, so that his face remained entirely uncovered.”

Even if we accept the above example as atypical, perforation of the visor created a point of weakness. De la Marche recorded this exchange between John de Compais and Antoine de Vaudrey, fighting with estocs or thrusting swords at the pas de l’arbre de Charlemagne in 1443 “And finally de Vaudrey pierced the visor of his companion, and when de Compais felt it pierced, he threw his estoc with all his strength at the visor of his companion, and with that stroke they were both similarly taken in the visor. Each champion held the other by the pierced visor, and they lifted their swords so that both of them had their face naked and uncovered, and at that the judge threw down his baton, and had the guards restrain and separate them.”

It seems probable that both champions struck a blow that either glanced across the visor of their opponent until it reached a breath, or hit a breath directly. When it did the weapon point sank into the breath and lodged firmly.

At that point, there are a number of potential outcomes, and few of them favor the party struck. The point lodged in a breath may give an opportunity to lever a visor open. Alternatively, the striker may use the point lodged in his opponent’s helmet as a lever to put his opponent at a disadvantage.

Finally, a powerful thrust to the face could potentially stagger or even stun the target, particularly if it lodged in a breath so that it didn’t glance. Helmets were padded, but on most surviving helmets the padding was relatively thin, and much of the effectiveness of the padding depended on the way it also served as a suspension system. This was more effective against a downward impact than a horizontal blow to the face.

While a visor offered substantial protection, it was still a point of weakness compared to many other parts of the harness. Attacks against the visor were a logical attempt to exploit this vulnerability.