The cyclic variation of the number of sunspots was first observed by Heinrich Schwabe between 1826 and 1843 and led Wolf to make systematic observations starting in 1848 .
The first cyclic changes of sunspots was seen by Heinrich Schwabe , and made Rudolf Wolf study them carefully , starting in 1848 .
After Wilde 's play and Richard Strauss 's opera Salome , first performed in 1905 the erotic ` dance of the seven veils ' , became a standard routine in opera , vaudeville , film and burlesque .