Dan: While you're at it, check out my own abstract CI4 for the N.O.
meeting, where I describe gamma-ray spectra obtained from dirt filtered
from the air. Catch me at the N.O. meeting and I can give you some
useful advice.
Also, check out the Nov issue of The Physics Teacher for the article,
"Radioactive Balloon Measurements in Utah", which verifies my own work
with a balloon as described in The Physics Teacher, Vol. 33, 344 (1995).
This experiment is very instructive for students and the only detector
needed is a simple Geiger Counter. Filtering dirt out of the air with
a "ShopVac" is even better than using a balloon.
Tom Walkiewicz walkiewicz@edinboro.edu
Dept. Physics
Edinboro University
Edinboro, PA 16444