Economic historian John Steele Gordon returns to the pages of Barron’s this week to recount stories of technological innovations that turned out to be more “proof of concept” than practical invention.

The first iterations of a new technology can seem astonishingly clunky, at least in retrospect. Often, they are more a proof of concept than a practical device.

The first hydrogen bomb, detonated in 1952, was the size of a three-story house and weighed 82 tons. No airplane in the world could have carried it. Within little more than a decade, however, the thermonuclear warheads atop missiles were roughly the size of garbage cans and weighed less than 700 pounds.

A century and a half earlier, the first steam engines were very large and heavy relative to the power they produced. The big engines that drove the Philadelphia waterworks in the early 19th century — the largest steam engines in the country at the time — were built using James Watt’s low-pressure design. They had 32-inch cylinders with a stroke of six feet. But they only put out 12 horsepower. Even the more-efficient high-pressure engines, independently designed by Oliver Evans in the U.S. and Richard Trevithick in Britain, were bulky, and they were ravenous consumers of coal.

That was a big problem for the new steamships. The huge amount of coal they had to carry both limited their range and diminished the amount of cargo and passenger space available. The great Victorian engineer Isambard Kingdom Brunel conceived of a way out of the problem. Brunel knew that a ship’s carrying capacity increases as the cube of its dimensions, but the resistance of the water increases only as the square. So, build a steamship big enough, and it can go anywhere without refueling.

Brunel built the first steam-powered passenger ship capable of crossing the Atlantic entirely under steam, the SS Great Western. When launched in 1838, she was the longest steamship in the world at 236 feet. Brunel then built the SS Great Britain, launched in 1843, as the first truly modern ship: iron-hulled, steam-powered, and propeller-driven. She, too, was the largest ship in the world when launched, at 322 feet.

BRUNEL WAS NOTHING IF NOT A BIG THINKER. He decided to build a ship that could go from London to Sydney, Australia, and back without re-coaling. For this, however, he needed a leviathan. At nearly 700 feet long, the SS Great Eastern was not only the largest ship in the world when launched in 1858, but she remained unsurpassed in size for an astonishing 48 years, until the RMS Lusitania was launched in 1906.