ROCKPORT – Matthew Carter of Topsham owns Green Island Stone Work, and he spoke to the Rockport Garden Club at their regular meeting on Nov. 3 at the Rockport Opera House. Carter said he has been doing this program for garden clubs of Maine for the last seven or eight years. He covered the history of stone walls in New England, how to build them and the art and craft of dry stone walls.

Dry verses wet stone walls. What's the difference?

A wet stone wall is one built with cement mortar and lime based mortar before that. The cement mortar is wet when it goes on and dries to help hold the wall together, much like glue. Lime based mortar acts more as an insulator.

A dry stone wall uses only the stone's weight and friction to keep it together. Carter said that regardless of wet or dry, it's the construction that makes a wall strong to last a long time.

"Many people don't know that the early settlers that came from Europe really didn't have much stone to work with," said Carter. "What they did have was plenty of wood, but there is no evidence of dry stone walling before the Europeans."

Early settlers cleared the land and pulled out stumps and that's what they used as fences to help keep their livestock in check.

"What they didn't realize when they were pulling these stumps out was that they were unlocking a dormant supply of stone," he said. "The mess from the roots and the insulating dirt from the forest was what was keeping the stone on the bottom."

The Laurentide ice sheet, the giant ice sheet that covered the northern part of North America, basically dragged all the field stone we use for walls down from Canada.

"It was two miles thick in some places," he said "And sea level was 275 feet below where it is today. As the glacier receded we developed from six to eight feet of top soil over that stone. When the trees are growing, the roots hold the stone down."

What raises stone is frost.

"When the ground freezes, it heaves up and creates a void below, so when the muddy water drips down below the stone, the stone can never go down as far as it was the previous year and that's how year after year the stone comes up," he said.

In early agricultural journals and farming journals there was barely a mention about stone walls. That, said Carter, was before the New England crop of potatoes started to grow in farmer's fields.

"What happened was they really didn't think to use them as stone walls," he said. "There were stones around and they did use them to delineate the parcels they were given, but in general as the stones started to come up, they would pile the stones under the fences. They had a fence around a field and they needed to get rid of the stone for their plowing so they would put them around the edge. As the fences deteriorated the stone walls were [remained] there."

Those walls became to be known as tossed walls. An 1871 survey done by the U.S. government determined there was 252,539 miles of stone walls in New England.

How do you build a dry stone wall?

"As I said, gravity and friction are the only two forces that hold a wall together," said Carter. "A good stone waller will maximize those two forces while trying to keep up a reasonable pace. The foundation stones are usually the biggest ones, so the wall is wider at the bottom to accommodate that size."

Small stones are packed in between the stones. There should be about two inches difference in width between the foundation and the top.

"These small stones are called hearting," he said. "We don't just dump crushed stone in. We pack the hearting in there very tightly so the stones won't settle anymore. The first third of the wall is called the first lift and they are the bigger stones."

Carter said you need through stones as well. The stone is the width of the wall.

"A through stone ties the two sides of the wall together," he said. "About half way up we want a through stone for strength. On the second lift the stones are smaller because it's getting narrower at the top."

Carter said that one of the few principles that you have to stick to is called, "end in, end out." A nice through stone needs to traverse the width of the wall and not the length. He said novice builders might place a through stone length wise in the wall because it has a nicer face, but that does little to add to the strength. It needs to be placed across the wall to make it right. Placing the stone length wise is called trace walling.

"Another principle is the ‘one-over-two, two-over-one,’" Carter said. "A stone will bridge two stones and the ends of two stones will rest on one. We want to break those vertical joints and not have a one, over one, over one, over one. It creates fault lines and friction is not being used to its full potential."

Last comes the cap stones, which are basically through stones and serve to keep the animals and leaves out of the wall.

"To hear two dry stone wallers talk, we have our own glossary of terms," he said. "We use terms like tracers, batter boards, cheek ends, lunkies, sheep creeps, cover bends, smoots, middle bends and squeezes."

Dry stone walls, when done correctly, are built to last. Not just for years, but generations.

Carter has been building dry stone walls since 1992. Carter said that the lines between craftsmanship and art can blur when building walls. He said he likes to think of it as a craft.

Next up for the Rockport Garden Club according to Ann Robison, program chair for garden club, is the Holly Berry Fair that takes place in the Rockport Opera House on the first Saturday of December from 8 a.m. to noon