Q: I was walking along the shore of Pontoosuc Lake last week when the weather was warm and the water was low. I found a piece of dull blue glass about the size of a golf ball in the gravel. Could it be from an old glass furnace?

JANET, Pittsfield

A: It is slag, but without seeing it, I cannot be 100 percent sure, just 95 percent sure that isn't from a glass furnace, but rather from an iron furnace.

I believe it was during a reconstruction of Route 7 along the lake that iron slag, as it is called, was brought in as roadbed fill, at least in places. I asked around in the early 1960s, but never learned to what extent.

When I was science curator at the Berkshire Museum, I identified it for kids and adults who brought me samples. The clue that it is iron slag from one of the probably local former iron smelters is that it usually comes in either green or blue, sometimes brown, but almost always a dull, or muddy color. Slag from a glass works is glassy.

Here in the Berkshires, we had numerous ironworks and even several glassworks. I have found chunks of glass slag in Lenox Dale and Berkshire Village and just recently found a cache of iron slag on Constitution Hill in Lanesborough. It was used as fill along what is now an old wood road, but years ago was likely a well-used town road.

I would be surprised if there isn't iron slag in West Stockbridge, the Van Deusenville section of Great Barrington and Richmond, among other places in the Berkshires.


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Unfortunately, private property now restricts casual collecting.

Q: I want to hang a bird feeder for my aged grandmother. Can I only use one kind of seed to make it simple? If so, what would you suggest?

ALAN, Stephentown, NY

A: One of the best seeds to attract winter songbirds is black-oil sunflower seed, The smaller, softer-shelled black-oil is preferred by birds over the gray striped that is also available.

We once went through 40- or 50-pound quantities of gray striped sunflower seed years ago when the evening grosbeaks, now almost unheard of, spent their winters here.

Black-oil seeds will attract chickadees, nuthatches, a variety of finches - including goldfinches and purple and house finches - as well as cardinals, titmice, woodpeckers and more.

That answers your question, but I would also suggest that, rather than one type of seed, you try a good quality mixed bird seed to attract even more birds like tree sparrows and in fall, white-throated, white-crowned and chipping sparrows.

I would caution against mixed seed if English sparrows, doves or pigeons might pose a problem.

Questions and comments for Thom Smith: Email Naturewatch@live.com