Raphael Semmes, Memoirs of Service Afloat During the War Between the States

Modern ingenuity has suggested a beautiful mode of warming houses in winter. It is done by means of hot water. The furnace and the caldron are sometimes placed at a distance from the apartment to be warmed. It is so at the Observatory. In this case, pipes are used to conduct the heated water from the caldron under the Superintendent's dwelling, over into one of the basement rooms of the Observatory, a distance of one hundred feet. These pipes are then flared out, so as to present a large cooling surface; after which they are united into one again, through which the water, being now cooled, returns of its own accord to the caldron. Thus, cool water is returning all the time, and flowing in at the bottom of the caldron, while hot water is continually flowing out at the top. The ventilation of the Observatory is so arranged that the circulation of the atmosphere through it is led from this basement room, where the pipes are, to all parts of the building; and in the process of this circulation, the warmth conveyed by the water to the basement, is taken thence by the air, and distributed all over the rooms.

Now, to compare small things with great, we have, in the warm waters which are confined in the Gulf of Mexico, just such a heating apparatus for Great Britain, the North Atlantic, and Western Europe. The furnace is the torrid zone; the Mexican Gulf arid Caribbean Sea are the caldrons; the Gulf Stream is the conducting-pipe. From the Grand Banks of New Foundland to the shores of Europe is the basement—the hot-air chambers—in which this pipe is flared out so as to present a large cooling surface. Here the circulation of the atmosphere is arranged by nature, and it is such that the warmth conveyed into this warm-air chamber of mid-ocean is taken up by the genial west winds, and dispensed in the most benign manner, throughout Great Britain and the west of Europe. The maximum temperature of the water-heated air-chamber of the Observatory, is about 90°. The maximum temperature of the Gulf Stream is 86°, or about 9° in excess of the ocean temperature due the latitude. Increasing its latitude, 10°, it loses but 2° of temperature; and after having run three thousand miles toward the north, it still preserves, even in winter, the heat of summer.