Telluric screw of de Chancourtois, c 1862.

FRANCE - AUGUST 15: Model. In 1862 Béguyer de Chancourtois was the first person to make use of atomic weights to produce a classification of periodicity. He drew the elements as a continuous spiral around a cylinder divided into 16 parts. The atomic weight of oxygen was taken as 16 and was used as the standard against which all the other elements were compared. Tellurium was situated at the centre of his system, prompting de Chancourtois to name it the �Vis Tellurique�, or telluric screw. In 1869 Mendeleev published his first periodic table, the system of classifying the elements which is still used today. (Photo by SSPL/Getty Images)