Now, one day when, after a considerable auction, he had exhibited in his shop purchases more numerous than usual, I especially noticed some manuscripts in the Latin language, the paper, the writing and the binding of which denoted an Italian origin, and which might well be two hundred years old. The title of one was, I believe: _De Venenis_; of another: _De Viperis_; of a third (the present work): _De Dæmonialitate, et Incubis, et Succubis_. All three, moreover, by different authors, and independent of each other. Poisons, adders, demons, what a collection of horrors! yet, were it but for civility’s sake, I was bound to buy something; after some hesitation, I chose the last one: Demons, true, but Incubi, Succubi: the subject is not vulgar, and still less so the way in which it seemed to me to have been handled. In short, I had the volume for six-pence, a boon price for a quarto: Mr Allen doubtless deemed such a scrawl beneath the rate of type. That manuscript, on strong paper of the 17^{th} century, bound in Italian parchment, and beautifully preserved, has 86 pages of text. The title and first page are in the author’s hand, that of an old man; the remainder is very distinctly written by another, but under his direction, as is testified by autographic side notes and rectifications distributed all through the work. It is therefore the genuine original manuscript, to all appearances unique and inedited. Our dealer in old books had purchased it a few days before at Sotheby’s House, where had taken place (from the 6^{th} to the 16^{th} of December 1871) the sale of the books of baron Seymour Kirkup, an English collector, deceased in Florence. The manuscript was inscribed as follows on the sale catalogue: Nº 145. AMENO (_R. P. Ludovicus Maria_ [Cotta] de). De Dæmonialitate, et Incubis, et Succubis, _Manuscript._ _Sæc. XVII-XVIII._ Who is that writer? Has he left printed works? That is a question I leave to bibliographers; for, notwithstanding numerous investigations in special dictionaries, I have been unable to ascertain any thing on that score. Brunet (_Manuel du libraire_, art. COTTA d’Ameno) vaguely surmises his existence, but confuses him with his namesake, most likely also his fellow-townsman, Lazaro Agostino Cotta of Ameno, a barrister and literary man of Novara. “The author,” says he, “whose real Christian names would seem to be _Ludovico-Maria_, has written many serious works....” The mistake is obvious. One thing is sure: our author was living in the last years of the 17^{th} century, as appears from his own testimony, and had been a professor of Theology in Pavia.