HIDDEN WATER TRACED BY BOMB FALLOUT IN RAIN — Radioactive fallout from atom bomb tests can be used to seek out and “expose” new sources of drinking water that lie hidden deep in the earth…. Raindrops have an affinity for absorbing minute particles of tritium from the fallout left in the atmosphere after nuclear bomb tests. Scientists seek ways to use these particles as “atomic dog tags” to identify underground water and find out how it percolates into the earth, where it goes and how fast it travels. This, they believe, may be done by taking samples from test wells at different places and depths from which water “tagged” with tritium can be identified with delicate instruments to learn its origin as rain or snow.

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Ancient graffiti Regarding “Graffiti on the walls in Pompeii” (SN: 01/30/10, p. 14), I remember reading some years ago about graffiti being discovered in Pompeii. There was even a symbol that researchers interpreted as a sort of “Kilroy was here.” Is this an on­going study? New sites? I wonder if there were other markings, such as height marks recording children’s growth? The article says “written” — were all of the marks scratched into the rock? Bob Wilson, Oakridge, Ore. Graffiti were first observed at Pompeii in the late 19th century. More than 11,000 instances of graffiti have been found in the ancient city, about two-thirds of which has been excavated. Most consist of written messages scratched or incised on walls, with some drawings as well. These graffiti have attracted little scientific interest until recently. Graffiti research will continue, ...

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New weight for silver will not affect dimes — An atom of silver weighs less than previously thought, but this new finding of the National Bureau of Standards will not affect the silver dimes in your pockets. A dime will still be worth ten cents. The new atomic weight of silver was set at 107.873 through accurate measurements with a mass spectrometer. The atomic weight currently used is 107.880. The more precise atomic weight of silver may mean that the atomic weights of other elements may have to be adjusted.… What makes the new measurement significant is the fact that the mass spectrometer was calibrated to extraordinary accuracy through use of known mixtures of the two highly purified silver isotopes.

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