218 PERKINS, THOMAS, AND NIELSEN Table 4— PHYSICAL FORM OF ®!] AT VARIOUS DISTANCES FROM THE SOURCE Distance, miles 1317 present as a gas, % Sept. 4, 1963 onNonwre © > 99 Ne 73 90 92 92 96 + 10* Sept. 3, 1963 Oo8 © >99 82 82 81 58 + 20* 1 *The plus and minus values are the standard deviations. the use of short-lived natural tracers, which are produced by cosmicray spallation reactions, would be very useful, In investigations the natural presence in the atmosphere of cosmic-ray-produced *C1 (37.3 min) and *s (2.9 hr) was discovered. These radionuclides were found to be present in rainwater at concentrations that are readily measurable with the multidimensional analyzer. They are produced by cosmicray Spallation reactions on atmospheric argon. The concentrations of C1 and *S in six rains are recorded in Table 5 along with the concentrations of °°C1 (55 min), which was measured simultaneously. An additional spallation-produced radionuclide that is present in the atmosphere and can be readily measured in rainwater with the multidimensional spectrometer is “Na (15 hr). Its concentration in three rains is compared with that of ?*Na in Table 6. Table 5— CONCENTRATIONS OF THE COSMIC-RAY-PRODUCED RADIONUCLIDES %8C], 3S, AND 9Cl IN RAINWATER* . Date July July Aug. Aug. Aug. Aug. 29, 1964 30, 1964 1, 1964 1, 1964 12, 1964 18, 1964 Collection Dis/min per liter Volume, liters time, min 38C] 38S 39C] 5.10 6.64 3.5 1.8 2.2 10.0 50 15 50 10 5 40 147215 ~18 9+5 31+12 42+13 55 +9 1325 4+ 2 + fT ~7 t 200 + 17 ~10 15 +3 2825 62+ 12 53 + 3 *The plus or minus values are the standard deviations. +Not measured.