STONE BY STONE, by Robert M. Thorson, Walker & Company, New York, 2002, $14.

The subtitle on the cover proclaims “The Magnificent History in New England’s Stone Walls.” The first time around I read “of” instead of “in” and the difference is striking. “Of,” of course, refers to the history of stone walls. “In,” on the other hand, steers the reader to the history of each type of stone making up the walls, as well as the walls themselves.

The author is a professor of geology at the University of Connecticut and the early chapters discussing the formation of the rock on the Earth’s surface, continental drift, and effects of the Ice Age may remind some of a geology text. At times they read at glacial speed.

In fact, as a belated New Year’s resolution, the reader might want to remind oneself that it is occasionally good to read books that require us to stretch. Think of it as a meal. If you eat your spinach, Mom will give you dessert. Thorson serves up plenty of steak and mashed potatoes between the spinach and dessert. He also gives the reader a painless excursion into the region’s agricultural history.

We learn that rocks did not appear on the surface in many areas until the forest was cleared and the land began to be worked. Even then it wasn’t the farmer’s plow that pulled the rocks to the surface as much as the action of water and the freezing and thawing of the soil.

In New England, fields were small because it was easier to haul the rocks a shorter distance. Consider the author’s calculation of the amount of walking necessary to clear a square field containing 100 stones per acre. Carrying one stone at a time required the farmer to walk 58 miles to clear an 8-acre field while walking only 20 miles to clear eight 1-acre fields.

Most stone walls in New England didn’t start out as walls. In Colonial times, they were simply rock dumps on the edges of fields. Fences to confine cattle were, more often, built of the plentiful wood supplied by the clearing of the forests. The good economic times of the 1820s and early 1830s contributed mightily to the building of real stone walls. During that period many a stone dump became an orderly wall as the farmer had the economic resources to add symmetry to the homestead.

Who has not traveled the byways of New England, particularly its three northern states, and wondered about the people who built the shattered strings of stone that trail off up a hill and disappear into the trees? The answer lies in a rural history that many of us have forgotten. In 1840, half of the land in New Hampshire had been cultivated. By 1870, the figure was reduced to 39 percent and was falling with each successive decade. Maine and Vermont had similar occurrences.

Where did they go, the people who fought the land for a meager living? Quite simply, many moved to the burgeoning cities of the region to work in the mills. The Civil War took many a scion of a hill-farm family and showed him a thousand different sights and places. Many others headed west where the land grew, instead of rocks, grass as high as a man’s head, on flat land at that.

In 1871 a fencing census estimated the length of New England rock walls to be 240,000 miles. What happened to them? The demand for better roads between farm and town led to the demise of many a wall. The rock crusher, invented in 1852, was made portable in the last decades of the century. A farmer could sell his rock wall for highway construction, replace it with recently invented barbed wire and make a profit on the transaction.

There is a myth that stone walls will last forever. The author spends a fair amount of time throughout the book explaining why it isn’t so. The leading reasons are the impact of frost’s annual incursion under the wall as well as the constant action of rain and sun working on the individual stones .

Robert Frost in “Mending Wall” wrote:

Something there is that doesn’t love a wall,

That sends the frozen-ground-swell under it

And spills the upper boulders in the sun

Frost was succinct. You learn a whole lot more by reading Robert Thorson.

Chuck Veeder can be reached at veederc@surfbest.net.