Emilé Doumergue's Biography of John Calvin

Loraine Boettner has noted (Calvinism in History)that "beyond comparison the most exhaustive and authoritative work ever published on [John] Calvin" is Emilé Doumergue's (1844-1937) massive seven-volume biography written in French, Jean Calvin: Les hommes et les choses de son temps (1899-1927). Jean-Daniel Benoît, author of Jean Calvin: La Vie, l'homme, la pensée (1933), describes his own biography (only 275 pages) as constituting "the quintessence of the seven big volumes of my old master, dear Emile Doumergue."

Although it has never been translated into English (except for brief portions here and there), Domergue's seven-volume biography is -- happily for those who read French -- available to read online:

Vol. 1
Vol. 2
Vol. 3
Vol. 4
Vol. 5
Vol. 6
Vol. 7

In the course of preparing this blog post, I came across an undated letter by Doumergue which was for sale at auction which includes the following remarks (translation provided by the auctioneer):

" ... So what has caused you to know my name, is my work on Calvin, - a work of which seven volumes have appeared and of which the eighth and last volume without doubt will appear shortly; it is finished ... "

This raises a question which I would love to clarify. Is there, in fact, an eighth and final volume which has never been published? If so, does it exist in manuscript somewhere? Inquiring minds, who consider Doumergue to be the premier biographer of the premier theologian of the Reformation, would like to know.