Evolution of "diverse"

In Will and Ariel Durant’s Story of Civilization series, the word “diverse” has been spelled “divers” all but one time, in the middle of The Age of Louis XIV , which was published in 1963. A few pages later it went back to being “divers” and so far, in Rousseau and Revolution, published in 1969, it’s still “divers.” Was there an evolution in the word’s spelling over the last thirty years, or did the Durants just misspell it?

My dictionary shows slightly different meanings.

Diverse: 1)different, dissimilar: 2)varied, diversified

Divers: 1)several, various; 2)[Archaic}diverse