Page "Vladimir Markovnikov" Paragraph 4

Although he published mostly in Russian which was not understood by most Western European chemists, the 1870 article in which he first stated his rule was written in German.

However the rule was included in a 4-page addendum to a 26-page article on isomeric butyric acids, and based on very slight experimental evidence even by the standards of the time.

Hughes concludes that the rule was an inspired guess, unjustified by the evidence of the time, but which turned out later to be correct ( in most cases ).