I won't tell you who he is. At least not yet. The apparatus on the table might give a hint. And the apparent serenity of the portrait did not always describe the man's life.
He was widely acknowledged in his time as a popular public speaker. Here is a description by a person who attended his lectures:
He was completely master of the situation; he had his audience at his command, as he had himself and all his belongings; he had nothing to fret him, and he could give his eloquence full sway. It was an irresistible eloquence, which compelled attention and insisted on sympathy. It waked the young from their visions and the old from their dreams. There was a gleaming in his eyes which no painter could copy and which no poet could describe. Their radiance seemed to send a strange light into the very heart of his congregation; and when he spoke, it was felt that the stir of his voice and the fervor of his words could belong only to the owner of those kindling eyes...His enthusiasm sometimes carried him to the point of ecstasy when he expatiated on the beauty of nature, and when he lifted the veil from her deep mysteries.One gets the sense that he could have been a prodigious sermonizer, the proprietor of a megachurch, an Elmer Gantry of his time. And indeed he was a deeply religious man. But he was too humble to presume to speak directly for the Creator, too modest to claim to know the Creator's will. He was content to let the Creator's works speak for themselves. He was unsurpassed at reading the book of nature, that public scripture laid open for all to see. It was for him a book of wonders, revealed incontestably by the apparatus on the table -- the voltaic cells, the coils, the electrical machine, magnets and glass retorts.
His body then took motion from his mind; his hair streamed out from his head, his hands were full of nervous action, his lithe body seemed to quiver with eager life. His audience took fire with him, and every face was flushed. Whatever might be the after-thought or the after-pursuit, each hearer for the time shared his zeal and his delight; and with some listeners the impression made was so deep as to lead them into the laborious paths of philosophy, in spite of all the obstacles which the daily life of society opposes to such undertakings.Nothing, said Michael Faraday, is too wonderful to be true.