The Smithsonian, "first in the world, organized a comprehensive system of telegraphic meteorology, and has thus given first to Europe and Asia, and now to the United States, that most beneficent national application of modern science--the storm warnings." So much of value has been gathered by government surveys and by voluntary contribution that the institution has sent duplicates to various societies of specimens in geology, mineralogy, botany, zoölogy, and archæology, while it has remaining, "boxed up, varieties of art and nature" more than enough to twice fill the halls and galleries of the building. The work of Professor Henry grew more and more onerous, but he seemed to leave nothing undone. For many years he served gratuitously as chairman of the Lighthouse Board. When a substitute was needed for sperm oil, after almost numberless experiments, he showed that lard oil is the best illuminant, thereby saving the country over one hundred thousand dollars yearly, since 1865. During the last twelve years of his life, he devoted much time to our system of coast fog-signals, making "contributions to the science of acoustics, unquestionably the most important of the century." Observations were made, among other places, at Block Island and Point Judith. The distance between these fog-horns is seventeen miles, and the sound of one can be distinctly heard at the other when the air is quiet and homogeneous; but if the wind blows from one towards the other, the listener at the station from which the wind blows is unable to hear the other horn. While at work in the Lighthouse Depot, in Staten Island, December, 1877, Henry's right hand became in a paralytic condition. This foretold that the end was near. He died at noon, May 13, 1878, asking, with his latest breath, which way the wind came, as though still thinking how to save human lives in a fog at sea. He was buried May 16, at Rock Creek Cemetery, near Georgetown, D. C. He was ready when death came. Two weeks before, he said to a friend: "I may die at any moment. I would like to live long enough to complete some things I have undertaken, but I am content to go. I have had a happy life, and I hope I have been able to do some good." Several times during his connection with the Smithsonian Institution he was offered more lucrative positions, but he remained where he believed he could be most useful. He was called to the professorship of chemistry in the Medical Department of the University of Pennsylvania, with double the salary of his secretaryship; but he declined. He was urged also to take the presidency of the college at Princeton. John C. Calhoun desired him to accept a professorship in the University of Virginia, as there were so many difficulties in connection with the secretaryship. Henry declined, saying that "his honor was committed to the institution." Calhoun grasped his hand, exclaiming, "Professor Henry, you are a man after my own heart."