Price and Priestley moved in the same radical circles in London, while Priestley and Hume both welcomed him as a guest. He assisted at Voltaire’s masonic initiation. Pringle was a frequent travelling-companion in Europe; Walpole called on the two in Paris, where Franklin was a regular at d’Holbach’s salon. Casanova sat next to him, listening to him discussing aeronautical balloons with Condorcet (who also later persuaded him that slavery and racial inequality were corrupt). Lavoisier and Franklin fixed the lightning-conductors Franklin had invented to a Paris church; Boswell admiringly quoted him to Johnson.