The contents of the book were actual letters which had passed between the friends. It will be remembered that Harriet did not meet Mr. Atkinson during the progress of her mesmeric treatment and recovery from illness under his written advice. But soon after she got better, they were visiting together at the house of a cousin of hers, and during the six years or so which had since then passed, they had often met, and their correspondence had grown to be very frequent. Mr. Atkinson had gradually become the friend dearest to Harriet Martineau in all the world. He gained her affection (I use the word advisedly) by entirely honorable roads--by the delight which she took in observing his scientific knowledge, his originality of thought and his elevated tone of mind. But I cannot doubt that long before this volume of _Letters_ was published, he had become dear to her by virtue of that personal attraction which is not altogether dependent upon merit, but which enhances such merits as may be possessed by the object of the attachment, and somewhat confuses the relationship on the intellectual side. This condition of things is in no way especially feminine; John Stuart Mill bowed down to Mrs. Taylor, and Comte erected his admiration of Clotilde into a _culte_. Mr. Atkinson was many years younger than his friend, and very likely she never fully realized the depth of her own feelings towards him. But still the attraction had its influence, though unacknowledged in words, and unreciprocated in kind.