As we descend into the interior of the earth the temperature gradually increases. In mines, and during the sinking of artesian wells, it has been constantly observed that, at a certain distance from the surface, a point is attained at which the heat of summer anl the cold of winter produce no effect upon the temperature; and beyond this point the heat augments in a regular ratio of 1 Fah. for every 55! feet of descent. It is true that this increase of heat is not uniform in every part of the earth, as it differs in different strata at the same depth from the surface, but this variation is so small as not to affect the general rule. Reasoning from this data, geologists naturally conclude that at the depth of say 200,000 feet, the temperature must be 3,600—a heat which must keep all the materials in the center of the earth in a state of fusion. It is, therefore, taught by many, that the center of the earth is a fiery mass, and that the globe's solid crust does not amount to more than a fiftieth part of its diameter. But if this is a law or rule regarding the solid parts of the earth, the contrary seems to be the case with the fluid portions of it. Lieut. Berryman, U. S. N., in his deep sea soundings, seems to have eliminated a totally opposite law reigning in the ocean, viz., that the cold increases according to the depth; and in connection with this other remarkable phenomena. He says :— "Five hundred miles north of Bermuda we found the greatest reliable depth ever obtained, it being over four miles; and accompanying this were thermometrical observations of a singular character, indicating phenomena never before discovered or conceived, and which at this moment are an unsolved problem to the scientific world. In a long series of experiments the temperature was indicated as existing ten, fifteen, and twenty degrees below the freezing point. This may be owing to the defective instruments ; but if so, a consistency of error was preserved almost beyond tlie possibility of chance." The records of these deep sea soundings go to contradict the well-known and established law that water freezes at 32 Fah. ; also that there is one law relating to temperatures for the ocean and another for the dry land. There must have been some defect in the instruments referred to, which indicated an ocean temperature below the freezing-point, or else the stratum of fluid reached at the great depth mentioned was not common salt water, but some other fluid, incapable of freezing, except at a much lower temperature. We do not believe, however, that any such fluid exists where these deep sea soundings were taken.
This article was originally published with the title "Earth and Ocean Temperatures" in Scientific American 13, 19, 150 (January 1858)