    Sentence: How miany vector ‘equations did Heaviside and  Gibbs reformilate Maxwell's 20 scalar equtions nto?    Sentence 2: The origin of electric and magnetic fields would  not be fully explained until 1864 when James Clerk Maxwell  unified a number of earlier theories into a set of 20 scalar  equations, ‘were Tater reformulated Trto 4 vector  equations by Oliver Heavisideand Josiah Willard Gibbs.    