Letters.

Hot topic

"Newfound gas is greenhouse powerhouse" (SN: 7/29/00, p. 70) contains a common misconception about the greenhouse effect. It states, "The newly detected gas is chemically similar to sulfur hexafluoride--another strong absorber of solar radiation ..." (emphasis mine). While this statement may be true, it is irrelevant to the greenhouse efficiency of a gas. The mechanism of the greenhouse effect involves absorption of terrestrial radiation. A greenhouse substance admits incoming radiation, with its principal power density in the visible band, but stops the outgoing radiation, with its principal power density in the infrared band. This is why cars get so hot in the sun: The windows are transparent in the visible but not in the infrared.

Gerald A. Larson

Huntsville, Ala.

Sobering stories

I read with interest "Detoxifying desert manna" (SN: 7/29/00, p. 74). The understanding that traditional wisdom calls for detoxifying these legumes coupled with the fact that they are eaten nonetheless is indeed sad. The work of the agricultural scientists in making this staple safe to eat is vital. There is evident need for help from social science to get safe food practices accepted in the population.

Saul Cizek

Alexandria, Va.

Thank you for the article. Last year, while the epidemic in Ethiopia was rampant, we had planned an experiment with preventive medicine containing the nutrients that are deficient in grass pea and costing 3 cents per person per day, but no backer was found.