Over a series of long-distance phone calls, Meitner and Frisch came up with a simple experiment to bolster their claim: to measure the recoil of the fission fragments, using a Geiger counter with the threshold set above that of the alpha particles. Frisch conducted the experiment on 13 January, and found the pulses caused by the reaction just as they had predicted. He decided he needed a name for the newly discovered nuclear process. He spoke to William A. Arnold, an American biologist working with George de Hevesy, and asked him what biologists called the process by which living cells divided into two. Arnold told him that biologists called it fission. Frisch then applied that name to the nuclear process in his paper. He mailed both papers to Nature on 16 January; the jointly-authored note appeared in print on 11 February and Frisch's paper on recoil on 18 February.