Boltwood had conducted studies of radioactive materials as a consultant, and when Rutherford lectured at Yale in 1904, Boltwood was inspired to describe the relationships between elements in various decay series.
Boltwood realizou estudos de materiais radioactivos como asesor, e cando Rutherford daba clases en Yale en 1904, Boltwood foi inspirado a describir as relacións entre elementos en varias series de desintegración.