Richard Jordan Gatling (1818-1903), the inventor of the weapon that bears his name, had a passion for setting objects in orderly motion. His first invention was a four-bladed, screw-type ship’s propeller, for which he just missed establishing a patent. That was in 1836, when he was still a teenager. Over his long career he would devise a mechanical seed planter, a steam-powered plow, and a new and better flush toilet. Of the dozens of patents he registered, 18 were for agricultural implements. It might seem ironic that an enterprising farm boy from Murfreesboro, N.C., would end up inventing the first successful machine gun. But in fact, Gatling got the idea from the design of his own seed planter. If batches of seeds could be distributed and propelled into orderly furrows, why not bullets?

This isn’t the whole story, of course. In “Mr. Gatling’s Terrible Marvel” (Viking, 292 pages, $25.95), Pulitzer Prize-winning journalist Julia Keller argues that Gatling invented his murderous machine for humanitarian reasons. She makes a good, if not entirely convincing, case. Gatling, whom she calls the most “tender-hearted” of inventors, first offered his gun for sale to the Union Army in 1862 (though a Southerner, and raised on a slave-owning plantation, Gatling’s sympathies were with the North). Gatling never served in the war, but he’d seen wounded soldiers shipped home and was appalled by the slaughter. Like others at the time, he believed that hostilities would come to a quick end. But in April 1862, the Battle of Shiloh took place, registering 24,000 casualties, and that was followed in September by Antietam, still the single most lethal day of battle in American history. Fifteen years later, Gatling wrote to a friend, “It occurred to me that if I could invent a machine — a gun — which could by rapidity of fire, enable one man to do as much battle duty as a hundred, that it would, to a great extent, supersede the necessity of large armies, and consequently, exposure to battle and disease be greatly diminished.”

Such reasoning lies behind the modern strategy of “surgical strikes.” If one soldier with a Gatling gun can replace a dozen, risks may be minimized and — not coincidentally — costs reduced. The gun served as a deterrent, too: The mere threat of its awesome killing power made an adversary think twice. In one of the most bizarre episodes Ms. Keller recounts, on July 17, 1863, during the draft riots, the New York Times (which supported conscription) mounted three Gatling guns on the roof of its headquarters, with the editor in chief at the trigger, and successfully cowed an angry mob without firing a single shot.

Gatling’s hope that his invention would bring the Civil War to a speedy end did not materialize. Lieutenant Colonel James W. Ripley, chief of ordnance, had been besieged by cranks offering newfangled armaments and the Union Army rejected the weapon, despite promising test results. As Ms. Keller eloquently shows, the army was hidebound; it was always fighting the last war. The machine gun also threatened to destroy the romance of battle, and the generals on both sides clung to old ideals of valor. Where was the fabled glory of war if you simply mowed your enemy down rather than engaging him with sabers and matchlock rifles?

Despite Ms. Keller’s sympathy for Gatling, he remains shadowy in her account, a type rather than an individual. However sincere in wanting to end the war, he was also shrewd, self-promoting, and ambitious; his gun brought him a fortune, especially when he marketed it worldwide. This is, of course, part of his appeal: He was no mere “merchant of death” but a starry-eyed idealist and a shrewd pragmatist rolled into one. He was a new kind of human being, a distinctly American species. And his career in its spectacular ups and downs provides Ms. Keller with an opportunity for inspired digression.

Whether describing the role of the U.S. Patent Office — which made lively entrepreneurship possible — or the rattling state of Western roads and the combustible hazards of steamboats, or even the innards of Samuel Colt’s revolutionary six-shooter, she sets Gatling and his inventions in provocative context. This was an age when the newfangled came into its own; even Lincoln dabbled in invention. Things — what Walt Whitman called “the human-divine inventions, the labor-saving implements” — were the rage. Gatling, along with Edison and Morse and Colt (who acquired Gatling’s patent for the gun), enjoyed international celebrity. If his name lives on today only in shadowy opprobrium — or in the slang term “gat” — that is in large part because he was so disastrously successful.

His gun, the forerunner of the Maxim gun, the AK-47 and the Vulcan gun — the infamous “Puff the Magic Dragon” of the Vietnam War — consisted of six rifled barrels tightly bound in a metal ring and rotated by a hand-crank. It could shoot some 200 shells a minute. It saved the day for Teddy Roosevelt and his Rough Riders at the Battle of San Juan Hill, with “Machine Gun” Parker manning the barrage. But it also massacred strikers and was the weapon of choice in colonial skirmishes, both in America and Africa. It was, as Ms. Keller bluntly puts it, a “tool of racism,” ideal for annihilating “natives,” but faintly dishonorable when turned on fellow Europeans — at least until World War I. It was a ghastly marvel of ingenuity that changed our world forever.

eormsby@nysun.com