One Good Turn: A Natural History of the Screwdriver and the Screw (5 page)

A technical work that predates both Agricola and Ramelli is the so-called
Medieval Housebook.
This handwritten manuscript, whose author and exact provenance are unknown, is thought to come from southern Germany. It has been described as a household manual for a knight’s castle, a common genre at the time.
⁶
In its present state the book consists of sixty-three parchment leaves, beautifully illustrated and covering a variety of subjects: jousting, hunting, warfare, courtship. Astrological horoscopes describe traits of people born under the sign of different planets: the regal Sun, amorous Venus, warlike Mars. Industrious Mercury is accompanied by a variety of craftsmen: an organ builder; a goldsmith, wearing eyeglasses and hammering out a beaker; and a clockmaker. I examine the drawing through a magnifying glass, helpfully provided by the Frick Collection in New York City, where a traveling exhibition of selected pages from the
Housebook
is on display. I’m hoping to find a screwdriver on the clockmaker’s workbench, but no luck. The section on smelting includes a water-powered device for working bellows, but there is
no indication that screws were used. Further on, several pages are devoted to the technology of war. I pore over each drawing in turn, under the watchful eye of an increasingly suspicious museum guard.

Among the intricate drawings of cannons, battle wagons, and scaling ladders, I find a collection of miscellaneous hardware: an auger, assorted manacles, and mysteriously shaped crowbars that the caption describes as tools for forcing apart iron gratings—ancestors of Ramelli’s portcullis twisters. Although the
Housebook
drawing shows a wrench, there is no screwdriver. But there is something almost as good. Two of the devices—a leg iron and a pair of manacles—are fastened with slotted screws.

The exact date of the
Housebook
is unknown. Most scholars believe that it was written between
1475
and
1490
, almost a century earlier than the books of Agricola and Ramelli, and more than three hundred years before the
Encyclopédie.
Since the author of the
Housebook
included a separate drawing of a screw, one might guess that screws were a novelty. Interestingly, the screws in the
Housebook
are used to join metal, not wood. Such screws must mate with threaded holes, so these fifteenth-century screws were made with a relatively high degree of precision.

I have not found a screwdriver, but I have found a very old screw. Surely slotted screws were used for
something less specialized than attaching leg irons and manacles? I go back to Dürer. Although his religious and allegorical engravings rarely include mechanical devices, an exception is his last etching, made in
1518
. The subject is a cannon. It is being towed through a pastoral countryside, the roofs of a peaceful village visible in the valley below. The contrast between the artillery piece and the idyllic landscape is dramatic. This is also a comment on the mechanization of war, for the scene includes a glum-looking group of Oriental warriors holding swords and pikes. Dürer renders the cannon, its wooden carriage, and the two-wheeled limber in great detail. However, the iron parts of the cannon, including a complicated elevating mechanism, are not attached to the wooden frame with screws but with heavy spikes.

Dürer’s etching gives me an idea. Weapons have often been the source of technological invention. Radar and the jet engine, which both originated during the Second World War, are two modern examples. The most dramatic military innovation of the Renaissance was the gun. The first guns were bombards, short heavy mortars firing stone balls. Bombards were fixed to wooden platforms and were dragged from place to place only with great difficulty. Before the end of the fifteenth century, however, bell foundries cast bronze barrels, about eight feet long, that were light enough to be mounted on a wheeled carriage and were fully mobile.
One of these innovative weapons is the subject of Dürer’s etching.

Before casting full-size cannons, foundries experimented with small portable weapons. The oldest surviving example of such a “hand-cannon” is a one-foot-long bronze gun barrel, made in Sweden in the mid-
1300
s.
⁷
The barrel is attached to a straight wooden stock that the gunner either pressed against his body with his elbow or rested atop his shoulder like a modern antitank gun. Italians called the new weapon
arcobugio
(literally, a hollow crossbow). The Spaniards, who were leaders in gun-making, called it
arcabuz,
whence the French and English arquebus
.

Firing an arquebus was tricky. After loading the gun by the muzzle, the gunner had to balance the heavy weapon with one hand while holding a smoldering match to the touchhole or firing pan with the other. Even when a forked rest or tripod was used, it was difficult to aim properly. In addition, bringing one’s hand close to the priming powder was dangerous since there was always the risk of a premature explosion. Groups of arquebusiers waving burning matches while pouring gunpowder on their priming pans were likely to cause as much damage to themselves as to the enemy.

A solution to the firing problem was developed in the early
1400
s. A curved metal arm holding the match was attached to the stock. In the earliest versions, the gunner
manually pivoted the arm, gradually moving the match to the touchhole. Eventually, the movement was accomplished by a spring-operated mechanism, the so-called matchlock. The arm holding the match was cocked back, and when a button was depressed, a spring brought it down to the pan. In a further refinement, pressure on a lever-shaped trigger—a feature adapted from the crossbow—slowly lowered the match into the pan. Now the gunner had both hands free to steady and aim the gun. The modern firearm had arrived—lock, stock, and barrel.

The arquebus quickly became popular. In
1471
, the army of the duke of Burgundy counted
1
,
250
armored knights,
1
,
250
pikemen,
5
,
000
archers, and
1
,
250
arquebusiers.
⁸
By
1527
, in a French expeditionary force of eight hundred soldiers, more than half were arquebusiers.
⁹
Gunners were common soldiers. Technological innovation often trickles down from the rich to the poor; firearms evolved in the opposite direction. The first arquebuses were disdained by the nobility as unwieldy, and too inaccurate for hunting. Only in the late
1500
s did the gun become a gentleman’s weapon.

I go to the arms and armor gallery of the Metropolitan Museum of Art in New York City to see these early firearms for myself. In a glass case I find a matchlock made in Italy in the
1570
s. The gun is about three and a half feet long with an odd-shaped, curved wooden
stock that resembles a field-hockey stick. This type of gun, known as a petronel, was developed by the French, who called it a
poitrinal,
since the stock was shaped to rest against the
poitrine
(chest). Petronels were short-lived—as a skeptical English soldier pointed out, “fewe or none could abide their recoyling”—and they were replaced by guns with so-called Spanish stocks, which rested against the shoulder.
¹⁰

A musketeer firing his matchlock,
1607
.

The petronel in the Metropolitan is elaborately ornamented
and was obviously intended for hunting. The steel barrel and lock are engraved, and the stock is inlaid with carved bone. As I look closely at the decorations, my eye is drawn to the lock. The slotted heads of two screws are plainly visible. The lock is screwed—definitely screwed—to the stock.

Screws were probably used instead of nails to ensure that the lock was not loosened by the vibration of successive detonations. This use must have happened early, certainly before the
1570
s. Since there are no older matchlocks in the Metropolitan, I consult a well-known reference book,
Pollard’s History of Firearms.
I find a detailed view of a matchlock in a drawing made in Nuremberg in
1505
.
¹¹
The moving parts are fixed with rivets, but the mechanism itself is fastened to the stock with four screws, just like the petronel. In this exploded view the screws are shown in their entirety. They have round, slotted heads and threaded cores tapering to sharp points. The oldest depiction of a matchlock in
Pollard’s
is from a fifteenth-century German manuscript. The stubby weapon resembles a modern sawn-off shotgun. The short barrel sits in a wooden stock whose slightly angled butt suggests that the principle of transforming some of the shock of recoil into vertical movement was beginning to be understood. The precise drawing shows the right side of the gun. The lock is similarly attached to the stock with two slotted screws. The
manuscript is dated
1475
, about the same period as the
Medieval Housebook.
¹²
Here, at last, is a widespread application of early screws.

View of matchlock,
1505
.

During the
1500
s, the matchlock was replaced by a new type of lock—the so-called wheel lock. The wheel, which was on a spring, was wound up, or “spanned.” The key used to turn the wheel was called a spanner (which is what the English still call a wrench). When the trigger was pulled, the wheel turned rapidly against a piece of iron pyrites, producing a spark (the same principle as a modern cigarette lighter). The spark ignited the priming powder and the gun discharged. The piece of pyrites was held in a set of jaws that were tightened with small screws, and since it was necessary to regularly replace the worn pyrites, the gunner needed to have a screwdriver with him at all times. The solution was a
combination tool: the end of the spanner handle was flattened to serve as a screwdriver. This must be the “arquebusier’s screwdriver” mentioned in Diderot’s
Encyclopédie.

—

The matchlocks at the Metropolitan Museum are displayed in a small room that is part of a large area devoted to arms and armor. After examining the guns I decide to take a look at the armor. This is not research—I simply have fond boyhood memories of reading Ivanhoe and seeing the Knights of the Round Table at the movies. The centerpiece of the main gallery is a group of knights mounted on armored steeds. The armor, which was tinned to prevent rusting, is shiny. There are banners and colorful pennants, which give the display a jaunty, festive air; it is easy to forget that much of this is killing dress. The day I visit, the place is full of noisy, excited schoolchildren. I stop at a display case containing a utilitarian outfit, painted entirely black—not the Black Knight, just a cheap method of preventing rust. The beak-shaped helm has only a narrow slit for the eyes. “Neat!” the boy beside me exclaims to his companion. “It’s just like Darth Vader.”

The display is German armor from Dresden, dated between
1580
and
1590
. This is slightly later than what is generally considered to have been the golden age of armor, which lasted from about
1450
to
1550
. Contrary to
the movies of my boyhood, King Arthur’s knights, who lived in the sixth century, would have worn chain mail, not steel armor. Protective steel plates came into use only at the end of the thirteenth century. First the knees and shins were covered, then the arms, and by about
1400
, the entire body was encased. The common method of connecting the steel plates was with iron, brass, or copper rivets. When a small amount of movement was required between two plates, the rivet was set in a slot instead of a hole. Removable pieces of armor were fastened with cotter pins, turning catches, and pivot hooks; major pieces, such as the breastplate and backplate, were buckled together with leather straps.