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EDITOR’S NOTE: Following is an abridged version of Chapter 14 of “Adrift in America: Diary of a Minimalist Mariner,” a work found in the nonfiction section:

Center Ossipee, New Hampshire. May 23, 1990.

You think I’m kidding about bituminous concrete, but consider this: It’s all one huge piece.

About four years after moving into the truck and driving it over more than 10,000 miles of back roads, I find myself curious about how many miles of roadway have been laid across our country. So I take a trip from my grandmother’s house in Center Ossipee, where I am spending my second summer off the road, to the University of New Hampshire library about 50 miles away in Durham.

Here’s what I find:

First, the basics: Bitumen is the mineral grit of petroleum, the nonflammable component that remains as asphalt when everything else that easily evaporates or burns off is removed from petroleum. There is evidence that people around the Mediterranean were using asphalt from natural tar pits as binding and paving agents as early as 3800 B.C. But it wasn’t until nearly six millennia later, at the turn of the 20th century, that humans began manufacturing asphalt on an enormous scale that wasn’t so much mass production as mass byproduction. Asphalt is a byproduct of petroleum distillation. Kerosene, benzine, toluene and other volatile constituents of petroleum had found limited uses in the 19th century as lighting and cleaning fluids, but gasoline found its place in the 20th century. The automobile – the word literally means self-moving – is made mobile by a portable engine that derives its power from internal combustion, and the stuff that combusts is gasoline. The development of the automobile created a demand for gasoline that made petroleum refining a big business, but it also created a big problem: What to do with the residue, what to do with the sludge left in the bottom of the barrel after the gasoline, kerosene and other volatiles had been cooked off? An asphalt-based concrete, that’s what. Not only was there plenty of asphalt to bind together stone, crushed rock and gravel, but there were huge machines powered by internal combustion to spread the mixture around. In a sense, the gas-thirsty automobile invented the road that it rides on.

Now the facts: In this century, we Americans have spread bituminous concrete over nearly two million miles of public roads. It has been only natural to extend the blacktop into driveways, parking lots, shopping malls, residential subdivisions. I can’t find a reference book that will even estimate the amount of asphalt used in this off-road paving, but I’d be willing to bet it is at least half as much as the roads themselves.

Doing a little math: If all this blacktop were pieced together like a giant jigsaw puzzle, it would cover at least 20,000 square miles. Nine of our states are smaller than that. In fact, our hypothetical conglomerate of bituminous aggregate would cover all of Maryland, Delaware and most of New Jersey.

There’s another strange sense I get from studying bituminous concrete. Unlike portland cement, the concrete made from petroleum never quite loses its fluid quality. In a way, it’s like the material of America’s first great highways – its rivers and canals. Bituminous concrete flows like water, or, more appropriately, like a glacier, taking decades before its fluidity is apparent. North America’s most sought-after natural waterway, the Northwest Passage between the Atlantic and Pacific Oceans, wasn’t traveled entirely by ship until 1903-05, and even then, Norwegian explorer Roald Amundsen spent most of his two-year passage locked in ice. America’s first great manmade waterway, the Erie Canal between Albany and Buffalo, New York, was finished in 1825 but was useful less than a half century before railroads put it out of business. Building water canals required torturous excavations to depths that would accommodate boat drafts. Building bituminous concrete canals requires only superficial excavation because the fluid that is poured into them soon freezes into a surface that our internal combustion vessels can skim over, our destinations and urgencies too temporal for us to notice that our roadways too are moving. There is a modern Erie Canal, and it is called the New York Thruway. There are several modern Northwest Passages, and all of them bear interstate highway numbers.

Like one huge national canal, America’s bituminous concrete flows together. When we stand in our blacktop driveway, we are standing on one edge of a huge network of slowly flowing hydrocarbon that links us with the rest of the nation. Our driveway is connected to a street that flows into a larger road that then spills into even larger highways that branch off into smaller roads that separate into smaller streets that diffuse into other driveways – Aunt Tillie’s in Cape Cod or Uncle Ned’s in Washington State.

This huge network of bituminous concrete is a utility, like the telephone, electricity or natural gas systems, that is useful to all of us. It is especially useful to those of us whose homes are not at the back of the driveway but at the front.

– Sid Leavitt