Venus and Sun Spots

An interesting post for one and all at Tall Bloke's Talk Shop – see http://tallbloke.wordpress.com/2012/11/06/warren-de-la-rue-balfour-stewa… … sun spots appear to grow on the face of the Sun according to the positions of the planets Mecury and Venus as they orbit the Sun. Balfour Stewart was head of solar research at Kew Observatory in the late 19th century and the paper itself dates to 1872. Why does Venus in particular play a leading role in the production of sun spot activity?