It is rare to find a man like Dr. Coues, who was capable of incessant drudgery in the most prosaic technicalities, yet blessed with the poetic temperament and ardent imagination, able to array the deepest problems in a sparkling style which fascinated while it convinced. His literary labors would have killed most men, but to his grasp of mind nature had kindly joined a strong, healthy body that proved capable of any demand upon his physical endurance that his intellectual activity might make. He was tall, well-formed, classic in features, straight as an arrow, with the air of the scholar without the student's stoop, betraying no trace of mental weariness a man with the tastes of a sybarite and the soul of a poet; to quote from a leading journal, "the imagination of a Goethe and the research of a Humboldt."

In conversation he was fascinating, possessing much of the personal magnetism ascribed to James G. Blaine. It was the pleasure of the writer to have many interviews and to enjoy a somewhat intimate correspondence with him almost up to the time of his death.