In Drude's original paper he used ⟨ ⟨ v 2 ⟩ ⟩ instead of ⟨ ⟨ v ⟩ ⟩ 2 , and also accidentally used a factor of 2. This meant his result is L = 3 ( k B e ) 2 = 2.22 × × 10 − − 8 V 2 K − − 2 , which is very close to experimental values. This is in fact due to 3 mistakes that conspired to make his result more accurate than warranted: the factor of 2 mistake; the specific heat per electron is in fact about 100 times less than 3 2 k B ; the mean squared velocity of an electron is in fact about 100 times larger.