In ‘Pickle the Spy’ mention was frequently made of ‘Mademoiselle Luci,’ the mysterious young lady who, from 1749 to her death in 1752, was the French Egeria of Prince Charles. An exile, without a roof to cover his head in any land but the States of the Pope, to which he declined to go, the Prince was sheltered in the Parisian convent of St. Joseph by Mlle. Luci and the lady styled La Grande Main in the cypher of the Prince’s correspondence. By dint of some research, I discovered that Mlle. Luci was Mlle. Ferrand, while La Grande Main was her devoted friend, Madame de Vassé. Both were very intimate with a person always alluded to in the Prince’s correspondence as le philosophe. As Montesquieu lived in the same street (the Rue Dominique) as these ladies (who directed the Prince’s philosophical studies), as he was on friendly terms with Charles, Lord Elibank, Bulkeley, and other Jacobites, I concluded that the philosophe of the correspondence was probably the author of ‘L’Esprit des Lois.’ This was a blunder which criticism should have detected. The philosophe was not Montesquieu, but the Abbé Condillac. The proof is in the preliminary chapter of his ‘Traité des Sensations;’ he there dedicates that important psychological work to Madame de Vassé, and deplores the death of their beloved Mlle. Ferrand. Condillac, clearly, was their friend, le philosophe. Mlle. Ferrand, it seems, was the instructor of Condillac, as well as the protector and literary adviser of Prince Charles.

‘You know, Madame,’ says Condillac to Madame de Vassé, ‘to whom I owe the light which at length scattered my prejudices. You know what part she had in this book, that lady so justly dear to you, so worthy of your friendship and esteem. I consecrate my work to her memory, and I address you that I may share the pleasure of speaking about her and the pain of our common sorrow. May this book be the monument of your friendship, and preserve it unforgotten.’

A volume on the relations of sense and thought, like Condillac’s, is not the place to which one naturally turns in search of information about a girl who loyally served a proscribed Prince and a forsaken Cause. Yet it is Condillac who attests for us ‘the keenness, the just balance, of Mlle. Ferrand’s intellect, and the vivacity of her imagination, qualities apparently incompatible, when carried to the pitch at which she displayed them.’

The scheme of Condillac’s psychology cannot be discussed in this place, but he says that he owed everything to Prince Charles’s friend. ‘She enlightened me as to the principles, the plan, and the most minute details, and I ought to be the more grateful, as she had no idea of instructing me, or of making a book. She did not remark that she was becoming an author, having no design beyond that of conversing with me on the topics in which I was interested.... Had she taken up the pen, this work would be a better proof of her genius. But there was in her a delicacy which forbade her even to contemplate authorship.... This treatise is, unhappily, but the result of conversations with her, and I fear that I may have sometimes failed to place her ideas in their true light.’

Had Mlle. Ferrand survived, Condillac thinks that she would not have allowed him to acknowledge her influence on his work. ‘But how can I, to-day, deny myself the pleasure of this act of justice? Nothing but this remains to me, in our loss of a wise adviser, an enlightened critic, and a true friend. You, Madame, will share the pleasure with me, you who will not cease to regret her while you live.’ The philosopher speaks of ‘the intellect, the loyalty, the courage, which formed these ladies for each other.’ Loyalty, courage, wit, these women laid them at the feet of a Prince not their own, and solely recommended to their tenderness by his misfortunes.

‘Your friend, in dying, had this one consolation, Madame, that she was not to survive you. I have seen her happy in this reflection. “Speak sometimes of me with Madame de Vassé,” she said to me, “and let it be with a kind of pleasure.”’ Such was the girl, so brilliantly endowed, so brave, so affectionate, who did Prince Charles’s marketing, bought him novels and razors, directed his choice of books, was the channel through which his secret correspondence passed, was jealously regarded by his mistress, Madame de Talmond, and died before the end of all hope had come, before the Prince was renounced even by his own. To the angry Madame de Talmond she wrote, ‘I am strongly attached to your friend [the Prince] and for him would do and suffer anything short of stooping to an act of baseness.’

There must have been something in Charles, beyond his misfortunes, to win so much devotion from a woman of the highest intellect.

Mlle. Ferrand died, after a long illness, in October 1752. Her memory is preserved only by a note in Grimm’s correspondence, by the touching tribute of Condillac, and by the discovery of her kindness to a proscribed Prince. While she protected and advised him, she was inspiring a renowned philosopher, and keeping a secret which every diplomatist in Europe was eager to learn. We naturally desire to know whether Mlle. Ferrand was beautiful as well as talented and kind. But researches in France have not brought to light any portrait either of Mlle. Ferrand, or of Madame de Vassé, who long survived her friend, and was in correspondence, about 1760, with the Earl Marischal.[48]