I then thought that the greater activity of the natural minerals might be determined by the presence of a small quantity of a highly-radioactive material,different from uranium,thorium and the elements known at present.

• 我随后想到，天然矿石中较大的活性可能是因为其中含有少量的高放射性物质所致，这种物质不同于铀、钍或其他已知的任何元素。