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CARBONATE, SILICATE, EXPLICATE
Dear R/PS: In the January 1997 issue, page 16, while discussing the "carbonate-silicate cycle," the statement was made, "calcium carbonate is broken down into silicates, which are released as CO2 by volcanos." Because one does not get silicates or any other form of silica from carbonates, this statement has no meaning. Please tell me what actually does take place.
John H. Bigelow
St. Petersburg, FL
Editor's note: According to writer David Pacchioli, our reader is "quite correct." To better explain the carbonate-silicate cycle, he writes: "Atmospheric carbon dioxide dissolves in rain-water, forming a weak acid which dissolves silicate rock. The byproducts of this weathering – calcium ions, bicarbonate ions, and dissolved silica – are taken up by streams and rivers and carried to the ocean, where snails and other organisms use them to make calcium carbonate shells and silica shells. When buried shells are heated at depth, this process is roughly reversed, as the cited article correctly states. But calcium carbonate is not Obroken down into silicates, which are released as CO2 by volcanoes.' Instead, when heated, calcium carbonate and silica are recombined into silicate minerals, releasing CO2 in the process."
KEEPERS
Dear R/PS: The January 1997 issue is a treasure. I've been a long-time admirer of Hector Flores' work with Peruvian farmers, and I think you did a wonderful job writing about the project. The visuals accompanying the article were beautiful as well: the traditional paint-ings created throughout centuries in many Andean countries, including my beloved Colombia, are always full of color and meaning.
Carmen Millon de Benevides
University Park, PA
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MAC'S DAD IN PARADISE
Dear R/PS: It was with great surprise and pride that I read the article "Pigs in Pa-radise" in the January 1997 issue. Pride because it featured my son, James "Mac" McIntyre as well as Douglas Greger. David Pacchioli is to be commended on his writ-ing of this most educational and entertaining article. I have heard this fantastic story as well as seen the videos, many times, and he has captured all the excitement and, yes, danger of such an undertaking. It should be noted that the photographs of the chief and the pigs were taken by Mac.
Robert S. McIntyre
Colonia, NJ
CORRECTION
The drawings reproduced on pages 3 and 5 of the January 1997 issue of Research/Penn State should have been accompanied by an acknowledgment that each was based on a photograph. According to Caroline Joan S. Picart, who wrote the essay "Inside Notes from Outside,"
the image on page 3 was based on "Bold venture into night" by the fashion photographer Hiro, first published in Harper's Bazaar in October 1963 and widely reproduced subsequently. The drawing on page 5 was based on a Reuters news photograph published in the Korean Times in 1993. Research/Penn State regrets the omission.
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