The high temperature of the Bath springs, their saline character, and their content of radioactive substances all combine to show that the waters must rise from a great depth. If we take the average temperature of normal spring water at 50° F. and that of the Bath Springs at 120° F., this gives an excess of 70° above the normal. Accepting the usual temperature gradient in England as being 1° F. for every 64 feet of depth, this makes the position of the: ultimate source 4,480 feet below the surface. This figure must, however, be regarded as a minimum, since no allowance is here made for cooling on ascent. This is an unknown factor, and sufficient data are not available for a reliable estimate. In any case the depth is unlikely to be less than 5,000 ft. and is probably far greater. This water, then, is obviously something very unlike the ordinary surface springs fed by atmospheric waters circulating in the upper layers of the earth's crust.